FDA v. Wages and White Lion Investments, LLC (604 U.S. 542, 2025)

PRELIMINARY PRINT Volume 604 U. S. Part 2 Pages 542–592 OFFICIAL REPORTS OF THE SUPREME COURT April 2, 2025 Page Proof Pending Publication REBECCA A. WOMELDORF reporter of decisions NOTICE: This preliminary print is subject to formal revision before the bound volume is published. Users are requested to notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, pio@supremecourt.gov, of any typographical or other formal errors. 542 OCTOBER TERM, 2024 Syllabus FOOD AND DRUG ADMINISTRATION v. WAGES AND WHITE LION INVESTMENTS, L. L. C., dba TRITON DISTRIBUTION, et al. certiorari to the united states court of appeals for the fth circuit No. 23–1038. Argued December 2, 2024—Decided April 2, 2025 This case concerns whether the Food and Drug Administration (FDA) law- fully denied respondents authorization to market certain electronic nico- tine delivery system products—known as electronic cigarettes, e- cigarettes, or vapes. These products have rapidly gained popularity during the past 20 years, offering existing smokers a potentially safer alternative to traditional combustible cigarettes. But e-cigarettes carry their own health risks, and the panoply of available favors—which include not only traditional cigarette favors (like tobacco and menthol) but also fruit, candy, and dessert favors—appeals to non-smokers, par- ticularly younger Americans. The FDA has long had the responsibility to determine whether manu- Page Proof Pending Publication facturers may market new drugs, but it was the passage of the Family Smoking Prevention and Tobacco Control Act of 2009 (TCA) that frst gave the FDA broad jurisdiction to regulate tobacco products. Al- though the Act barred the FDA from banning all regulated tobacco products outright, see 21 U. S. C. § 387g(d)(3), it prohibited a manufac- turer from marketing any “new tobacco product” without FDA authori- zation, see § 387j(a)(2)(A). One pathway to authorization of a “new tobacco product” is the submission of a premarket tobacco product appli- cation. See § 387j(c)(1)(A)(i). The TCA requires the FDA to deny such an application unless an applicant shows that its product “would be ap- propriate for the protection of the public health.” § 387j(c)(2)(A). To determine this, the FDA must consider, among other things, “the risks and benefts to the population as a whole” and “tak[e] into account” the likelihood that users of existing tobacco products will stop using those products and that non-users will start using them. § 387j(c)(4). In 2016, in response to the surging youth demand for favored prod- ucts, the FDA deemed e-cigarettes “tobacco products.” Given that most e-cigarette products were not marketed in the United States be- fore February 15, 2007, the vast majority of these products qualifed as “new tobacco products” under the TCA. Most manufacturers of e- cigarette products would thus need to comply with the TCA's premarket-authorization regime to sell their products. This made the Cite as: 604 U. S. 542 (2025) 543 Syllabus continued sale of most e-cigarette products illegal absent authorization. So to give these manufacturers adequate time to submit premarket to- bacco product applications, the FDA delayed enforcement for two to three years. See 81 Fed. Reg. 28977–28978. This permitted e- cigarette products to remain on the market while manufacturers fled their applications. A Federal District Court ultimately imposed a deadline of September 9, 2020, for applications. In the lead up to the application deadline, the FDA issued numerous forms of guidance concerning premarket tobacco product applications that orbited around four central themes: (1) the types of scientifc evi- dence that would be required; (2) the importance of cross-product com- parisons and investigations; (3) the FDA's enforcement priorities with respect to device type; and (4) manufacturers' marketing plans, which were described as “specifc restrictions on sale and distribution” meant to deter new smokers from taking up e-cigarette products. App. 27. In 2019, the FDA proposed a rule related to the submission of premar- ket tobacco product applications, and the proposed rule distilled the four topics discussed in the predecisional guidance. See 84 Fed. Reg. 50566, 50580, 50581, 50585, 50603. Respondents submitted applications seeking approval to market and sell favored e-liquids for open-system e-cigarettes. The FDA denied Page Proof Pending Publication respondents' applications, concluding they had not provided suffcient scientifc evidence to demonstrate that the marketing of their products would be appropriate for the protection of public health. Specifcally, the FDA held respondents had not provided evidence from a randomized controlled trial, longitudinal cohort study, or other “robust and reliable” evidence that their dessert-, candy-, and fruit-favored products had benefts over tobacco-favored products. Despite previously describing marketing plans as “critical,” the FDA decided “for the sake of eff- ciency” not to evaluate respondents' marketing plans. To each denial order, the FDA appended a “Technical Project Lead (TPL) Review.” See App. to Pet. for Cert. 177a, 285a. These lengthy documents, which canvass the scientifc literature on youth e-cigarette use, refect the FDA's evolving understanding of how favor, regardless of e-cigarette device type, drives youth smoking initiation and nicotine addiction. Respondents petitioned for judicial review of the FDA's denial orders under the Administrative Procedure Act (APA). See § 387l(b) (citing 5 U. S. C. § 706(2)(A)). The Fifth Circuit, sitting en banc, granted re- spondents' petitions for review and remanded to the FDA. The en banc majority held that the FDA had acted arbitrarily and capriciously by applying application standards different from those articulated in its predecisional guidance documents regarding scientifc evidence, cross- favor comparisons, and device type. The court expressed particular 544 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Syllabus concern about the FDA's failure to review marketing plans it previously deemed critical. It also rejected the FDA's argument that any errors were harmless. Held: 1. As a preliminary matter, the Court declines to reach and thus ex- presses no view on respondents' argument that the FDA erred in evalu- ating respondents' applications under standards developed in adjudica- tion rather than standards promulgated in notice-and-comment rulemaking. This complicated question sweeps beyond the question presented and lacks adequate briefng. P. 565. 2. The Fifth Circuit's conclusion that the FDA acted arbitrarily and capriciously in its adjudication of manufacturers' premarket tobacco product applications is vacated because the FDA's denial orders were suffciently consistent with its predecisional guidance—as to scientifc evidence, comparative effcacy, and device type—and thus did not run afoul of the change-in-position doctrine. Pp. 566–586. (a) The Court analyzes the Fifth Circuit's conclusion that the FDA acted arbitrarily and capriciously under the change-in-position doctrine, which provides that “[a]gencies are free to change their existing policies as long as they provide a reasoned explanation for the change,” “ `display Page Proof Pending Publication awareness that [they are] changing position,' ” and consider “ `serious reliance interests.' ” Encino Motorcars, LLC v. Navarro, 579 U. S. 211, 221–222 (quoting FCC v. Fox Television Stations, Inc., 556 U. S. 502, 515). This doctrine asks two questions: frst, whether an agency changed existing policy, and second, whether the agency displayed awareness of the change and offered good reasons for the new policy. Pp. 566–571. (b) The FDA's denial orders were suffciently consistent with its predecisional guidance regarding scientifc evidence. The TCA states that either “well-controlled investigations” or other “valid scientifc evi- dence” if found “suffcient” may support a fnding that a new tobacco product is “appropriate for the protection of the public health. ” §§ 387j(c)(5)(A)–(B). The TCA thus left the FDA broad discretion to de- cide what sort of scientifc evidence an applicant was required to submit. Across its various guidance documents, the FDA's main point was that manufacturers who failed to submit evidence based on “well-controlled investigations” would need to provide rigorous scientifc evidence that the sale of their particular products would be appropriate for the protec- tion of the public health. The applicants did not submit randomized controlled trials or longitudinal cohort studies, so the fate of their appli- cations turned on whether they submitted “other evidence” that met the FDA's standard of scientifc rigor and relevance to their product. Cite as: 604 U. S. 542 (2025) 545 Syllabus The FDA rejected respondents' applications because that test was not met. As evidence of a change in position, respondents point to the FDA's July 9, 2021, internal memorandum, which stated that the failure to submit evidence from a randomized controlled trial or longitudinal cohort study would constitute a “fatal faw” that would “likely” result in denial of an application. But the FDA issued a superseding memo- randum, which recognized that “other evidence” may demonstrate a product is “appropriate for the protection of the public health,” and the FDA represents that it did not rely on the July 9, 2021, internal memo- randum when adjudicating applications—a representation afforded a presumption of regularity. Pp. 571–578. (c) The FDA's comparative-effcacy requirement was not inconsist- ent with its predecisional guidance. The TCA expressly contemplates comparisons of different tobacco products, and the FDA's guidance elab- orated on the types of comparisons that would be helpful. The FDA's 2019 guidance recommended that a manufacturer “compare the health risks of its product to both products within the same category and subcategory, as well as products in different categories as appropri- ate,” and its 2020 enforcement guidance telegraphed the FDA's view that dessert-, candy-, and fruit-favored products were more likely than tobacco- and menthol-favored products to appeal to the young. Page Proof Pending Publication Thus, when the FDA denied respondents' applications for failing to dem- onstrate the beneft of their favored products over tobacco-favored products, it was following a natural consequence of its predecisional guidance. Pp. 578–582. (d) The FDA's treatment of device type did not violate the change- in-position doctrine. The FDA's 2020 guidance did not establish a “safe harbor” for non-cartridge-based products. Although the 2020 guidance emphasized the FDA would prioritize enforcement against cartridge- based products, it stated the FDA would also prioritize enforcement against manufacturers “whose [products'] marketing is likely to promote use by . . . minors.” That latter category seemingly covers respond- ents' products. Even if the FDA had changed its position in this re- spect, it offered “good reasons,” namely, evidence showing that youth demand had moved from favored cartridge-based products to favored disposable products. Fox Television, 556 U. S., at 515. From that evi- dence, the FDA drew the reasonable inference that youth were most strongly drawn by favor rather than device type. Pp. 582–586. 3. The Fifth Circuit relied on an overly broad reading of Calcutt v. FDIC, 598 U. S. 623 (per curiam), to reject the FDA's claim of harmless error regarding the agency's change of position on marketing plans. The FDA does not contest that despite assuring manufacturers that marketing plans would be “critical” to their applications, the FDA ulti- 546 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Syllabus mately did not consider respondents' marketing plans. The FDA ar- gued below that any error in this respect was harmless error because it issued denial orders to other manufacturers after reviewing marketing plans that were materially indistinguishable from respondents'. The Fifth Circuit rejected the FDA's harmless-error argument, relying on this Court's decision in Calcutt for the proposition that “APA errors are only harmless where the agency would be required to take the same action no matter what. In all other cases, an agency cannot avoid re- mand.” 90 F. 4th 357, 390. The Court agrees with the FDA that the Fifth Circuit read Calcutt too broadly. That said, the proper standard presents a diffcult prob- lem, requiring reconciliation of the so-called remand rule developed in SEC v. Chenery Corp., 318 U. S. 80, 88, 93–95, with the APA's instruc- tion that reviewing courts must take “ `due account' ” of “ `the rule of prejudicial error' ” that “ordinarily appl[ies] in civil cases,” Shinseki v. Sanders, 556 U. S. 396, 406 (quoting 5 U. S. C. § 706). The most natural interpretation of the APA's language is that reviewing courts should adapt the “rule of prejudicial error” applicable in ordinary civil litigation (also known as the harmless-error rule) to the administrative-law con- text, which, of course, includes the remand rule. In Calcutt, after recit- ing the remand rule in strong terms, the Court acknowledged that a Page Proof Pending Publication “remand may be unwarranted . . . [w]here the agency `was required' to take a particular action.” 598 U. S., at 630 (quoting Morgan Stanley Capital Group Inc. v. Public Util. Dist. No. 1 of Snohomish Cty., 554 U. S. 527, 544). Although the Fifth Circuit interpreted Calcutt's discus- sion to mean that there is only one exception to the remand rule, it has long been accepted that a remand may not be necessary when an agency's decision is supported by a plethora of factual fndings, only one of which is unsound, because a remand would be pointless. See, e. g., Massachusetts Trustees of Eastern Gas & Fuel Associates v. United States, 377 U. S. 235, 248. The existence of this exception is suffcient to show that the Fifth Circuit's reading of Calcutt went too far. That said, the FDA's reading of Sanders may also be excessive. The FDA has not asked the Court to decide the harmless-error question at this juncture, and the Court vacates and remands so the Fifth Circuit can decide the question afresh without relying on its overly expansive read- ing of Calcutt. Pp. 586–592. 90 F. 4th 357, vacated and remanded. Alito, J., delivered the opinion for a unanimous Court. Sotomayor, J., fled a concurring opinion, post, p. 592. Cite as: 604 U. S. 542 (2025) 547 Counsel Deputy Solicitor General Gannon argued the cause for petitioner. With him on the briefs were Solicitor General Prelogar, Principal Deputy Assistant Attorney General Boynton, Vivek Suri, Joshua M. Koppel, Catherine Padhi, Samuel R. Bagenstos, and Wendy S. Vicente. Eric N. Heyer argued the cause for respondents. With him on the brief were Joseph A. Smith and James C. Fraser.* *Briefs of amici curiae urging reversal were fled for the Common- wealth of Massachusetts et al. by Andrea Joy Campbell, Attorney General of Massachusetts, David C. Kravitz, State Solicitor, and Alda Chan and Matthew Lashof-Sullivan, Assistant Attorneys General, and by the Attor- neys General for their respective jurisdictions as follows: Kris Mayes of Arizona, Rob Bonta of California, Philip J. Weiser of Colorado, William Tong of Connecticut, Brian L. Schwalb of the District of Columbia, Anne E. Lopez of Hawaii, Kwame Raoul of Illinois, Aaron M. Frey of Maine, Anthony G. Brown of Maryland, Dana Nessel of Michigan, Keith Ellison of Minnesota, Matthew J. Platkin of New Jersey, Letitia James of New York, Joshua H. Stein of North Carolina, Ellen F. Rosenblum of Oregon, Page Proof Pending Publication Michelle A. Henry of Pennsylvania, Peter F. Neronha of Rhode Island, Charity R. Clark of Vermont, and Robert W. Ferguson of Washington; for Public Health, Medical and Community Groups by William B. Schultz, Andrew N. Goldfarb, and Dennis A. Henigan; and for Sixteen Members of Congress by Mark B. Samburg and Victoria S. Nugent. Briefs of amici curiae urging affrmance were fled for the Coalition of Manufacturers of Smoking Alternatives by Erik S. Jaffe; for Electronic Nicotine Delivery System Trade Associations et al. by Eric P. Gotting and Azim Chowdhury; for the Goldwater Institute by Timothy Sandefur; for Logic Technology Development LLC by Misha Tseytlin and Bryan M. Haynes; for R. J. Reynolds Vapor Company et al. by Noel J. Francisco, Donald F. McGahn II, Christian G. Vergonis, Ryan J. Watson, Andrew J. M. Bentz, Charles E. T. Roberts, and Charles R. A. Morse; for the Taxpay- ers Protection Alliance by Donald M. Falk and Erik S. Jaffe; for Thirteen Members of Congress et al. by Jordan Sekulow, Donn Parsons, and Ben- jamin P. Sisney; for Vaping Industry Stakeholders by J. Gregory Trout- man; for the Vapor Technology Association by Anthony L. Abboud; and for the Washington Legal Foundation by John M. Masslon II and Cory L. Andrews. Carter G. Phillips and Peter A. Bruland fled a brief for the Global Action To End Smoking, Inc., as amicus curiae. 548 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court Justice Alito delivered the opinion of the Court. This case concerns the efforts of the Food and Drug Ad- ministration (FDA) to regulate the sale of “e-cigarettes,” a product that rapidly gained popularity during the past 20 years. The governing federal law, the Family Smoking Pre- vention and Tobacco Control Act of 2009 (TCA), restricts the sale of all “tobacco products” that were not commercially marketed in the United States before February 15, 2007. Unless otherwise authorized, a manufacturer may not in- troduce such a product to the market until the FDA deter- mines that it is “appropriate for the protection of the public health.” 21 U. S. C. § 387j(c)(2)(A). In this case, we con- sider whether the FDA lawfully denied authorization to market certain favored e-cigarette products. I One of the FDA's longstanding responsibilities, dating Page Proof Pending Publication back nearly a century, is to determine whether manufactur- ers may market new drugs. For much of that history, the FDA lacked jurisdiction to regulate tobacco products. By the time Congress conferred that authority in 2009, a new product was ascendant on the market: the e-cigarette. This product offers existing smokers a potentially safer alterna- tive to traditional combustible cigarettes. But e-cigarettes carry their own health risks, and they come in a dizzying array of favors, many of which, such as dessert, candy, and fruit favors, are particularly appealing to the young. The surging youth demand for favored products—and the pros- pect of a new generation of smokers—caught the FDA on its back foot. In 2016, the agency declared that manufacturers of e-cigarette products would need to obtain the same mar- keting authorization that is required for other “tobacco prod- ucts.” The FDA's regulatory efforts culminated in the 2021 denial of over a million applications for favored e-cigarette products. The dispute before us arises from that mass denial. Cite as: 604 U. S. 542 (2025) 549 Opinion of the Court A The Pure Food and Drugs Act of 1906 was Congress's frst foray into the comprehensive regulation of food and drugs. The Act prohibited the interstate transportation of “any arti- cle of food or drugs which is adulterated or misbranded.” Ch. 3915, § 2, 34 Stat. 768. That Act also vested important responsibility in the precursor to the FDA, the Bureau of Chemistry in the U. S. Department of Agriculture. § 4, id., at 769. But early in its tenure, the Bureau disclaimed any authority to regulate tobacco products “labeled in such a manner as to indicate their use for” nonmedicinal purposes like “smoking or chewing or as snuff.” Dept. of Agriculture, Bureau of Chemistry, 13 Service and Regulatory Announce- ments 24 (Apr. 1914) (Feb. 1914 Announcements ¶13, Opinion of Chief of Bureau C. Alsberg). Congress later renamed the Bureau of Chemistry, frst as the Food, Drug, and Insecticide Administration and then as the FDA, the name by which we Page Proof Pending Publication know it today. A Historical Guide to the U. S. Government 249 (G. Kurian ed. 1998). In 1938, Congress enacted the Federal Food, Drug, and Cosmetic Act (FDCA), which vastly expanded the FDA's regulatory authority over “drugs and devices.” 52 Stat. 1049. One of the FDCA's major innovations was the estab- lishment of a system for premarket authorization under which manufacturers are prohibited from marketing “any new drug” in interstate commerce without the FDA's ap- proval. §§ 505(a)–(b), (d), id., at 1052; Historical Guide, at 251. To receive such authorization, manufacturers must prove to the FDA that their new products are safe for use. And if the FDA has “insuffcient information” to make that determination, it must “issue an order refusing” marketing authorization. § 505(d), 52 Stat. 1052. By the middle of the 20th century, nearly one in two Americans regularly smoked. See R. Rabin, A Sociolegal History of the Tobacco Tort Litigation, 44 Stan. L. Rev. 853, 855 (1992). Toward the latter half of the century, however, 550 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court the public became increasingly aware of the “great” “poten- tial hazard” of tobacco, Dept. of Health, Education, and Wel- fare, Surgeon General's Advisory Committee, Smoking and Health 25 (1964), and the addictive properties of nicotine, see L. Goitein, G. Chernack, G. Liu, & M. Davis, Developments in Policy: The FDA's Tobacco Regulations, 15 Yale L. & Pol'y Rev. 399, 402 (1996). The FDCA was enacted long before public awareness of the dangers of smoking became widespread, and neither its text nor its legislative history provided any indication that tobacco products fell within the FDA's jurisdiction. See A. Boeckman, An Exercise in Administrative Creativity: The FDA's Assertion of Jurisdiction Over Tobacco, 45 Cath. U. L. Rev. 991, 1015 (1996). Thus, during the frst 60 years after the FDCA's enactment, the FDA (like the Chemistry Bureau) repeatedly stated that it “lacked authority under the FDCA to regulate tobacco absent claims of therapeutic Page Proof Pending Publication beneft by the manufacturer.” FDA v. Brown & William- son Tobacco Corp., 529 U. S. 120, 144 (2000); see R. Kluger, Ashes to Ashes: America's Hundred-Year Cigarette War, the Public Health, and the Unabashed Triumph of Philip Morris 757–759 (1997) (Kluger). Tobacco regulation was largely left to Congress, which enacted various statutes between 1965 and the turn of the century to address the harms of tobacco use, including the imposition of warning requirements (15 U. S. C. §§ 1331, 1333, 4402(a)(1) (2000 ed.)); restrictions on the advertisement of certain tobacco products (15 U. S. C. §§ 1335, 4402(a)(2), (f) (2000 ed.)); requirements that the Secretary of Health and Human Services report on scientifc fndings about, among other things, “the addictive property of tobacco” (42 U. S. C. § 290aa–2(b)(2) (1994 ed.)); and age restrictions on the sale or distribution of tobacco products (42 U. S. C. § 300x–26(a)(1) (2000 ed.)). See Brown & Williamson Tobacco Corp., 529 U. S., at 137–139, 143–144. At no point during that period did Congress grant the FDA jurisdiction to regulate tobacco Cite as: 604 U. S. 542 (2025) 551 Opinion of the Court or tobacco products under the FDCA. And when the FDA tried via regulation to assert such jurisdiction in 1996, see 61 Fed. Reg. 44619–45318, this Court rejected that effort as beyond the FDA's statutory authority, see Brown & Wil- liamson Tobacco Corp., 529 U. S., at 126. Against that backdrop, Congress enacted the Family Smoking Prevention and Tobacco Control Act of 2009, 123 Stat. 1776. The TCA vests the Secretary of Health and Human Services, acting through the FDA, with the authority that this Court previously found lacking: namely, the power to regulate the manufacturing, marketing, sale, and distribu- tion of tobacco products. See § 901, id., at 1786. The TCA explicitly granted the FDA regulatory authority over “ciga- rettes, cigarette tobacco, roll-your-own tobacco, and smoke- less tobacco.” 21 U. S. C. § 387a(b). It also granted author- ity to regulate “any other tobacco products” that the FDA “by regulation deems” to meet the defnition of a tobacco product. Ibid. Page Proof Pending Publication The TCA's reach was broad. While the Act barred the FDA from banning all regulated tobacco products outright or requiring manufacturers to reduce nicotine yields to zero, see § 387g(d)(3), it prohibited a manufacturer from marketing any “new tobacco product” without FDA authorization, see § 387j(a)(2)(A). A “new tobacco product” is one that was not marketed in the United States before February 15, 2007, and the TCA subjected such products to a premarket authoriza- tion process. See §§ 387j(a)(1)(A), (a)(2). One pathway to authorization of the sale of a new tobacco product is the submission of a premarket tobacco product application.1 § 387j(c)(1)(A)(i). These applications require, 1 The TCA establishes a handful of other authorization pathways for new tobacco products. For example, manufacturers may ask the FDA to make a determination that a new tobacco product is substantially equivalent to a product commercially marketed as of February 15, 2007. See 21 U. S. C. §§ 387j(a)(2)–(3). And a showing of substantial equivalence may be un- necessary for new tobacco products that make only minor modifcations 552 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court among other things, information about a product's compo- nents and additives, the method by which it is manufactured, any proposed labeling, and an assessment of its health risks. See § 387j(b)(1). There are many reasons why the FDA may deny marketing authorization to a “new tobacco product,” but of main importance here, the agency must deny an ap- plication unless it is shown that the product “would be appropriate for the protection of the public health. ” § 387j(c)(2)(A). To determine whether a product meets this standard, the FDA must consider “the risks and benefts to the population as a whole” and “tak[e] into account” the “increased or de- creased likelihood” of two outcomes: frst, that the new prod- uct will induce users of existing tobacco products such as conventional cigarettes to stop using those products and, second, that “those who do not use tobacco products will start using” them. § 387j(c)(4). The FDA's determination Page Proof Pending Publication regarding the likely effects of a new product must, “when appropriate,” be based on “well-controlled investigations” or other “valid scientifc evidence” that is “suffcient to evaluate the tobacco product.” § 387j(c)(5). The FDA must act “[a]s promptly as possible” on a pre- market tobacco product application and “in no event later than 180 days af ter the receipt of an application. ” § 387j(c)(1)(A). If the FDA denies an application for pre- market authorization, “any person adversely affected” by the denial has 30 days to seek judicial review in a court of ap- peals. § 387l(a)(1). The reviewing courts must in turn apply the provisions of the Administrative Procedure Act (APA). § 387l(b) (citing 5 U. S. C. § 706(2)(A)). to products commercially marketed as of February 15, 2007. See § 387e( j)(3)(A). Moreover, manufacturers may seek authorization for “modifed risk tobacco products,” that is, products used “to reduce harm or the risk of tobacco-related disease associated with commercially marketed tobacco products.” §§ 387k(b)(1), (g)(1). Cite as: 604 U. S. 542 (2025) 553 Opinion of the Court B At the end of the 20th century, tobacco manufacturers tried without much luck to market safer alternatives to tra- ditional cigarettes, such as “smokeless” cigarettes. See Kluger 599–604; Dept. of Health & Human Servs., E- Cigarette Use Among Youth and Young Adults: A Report of the Surgeon General 9 (2016) (2016 Surgeon General's Re- port). But in 2007 a new product hit the American market: electronic nicotine delivery systems, which are popularly known as electronic cigarettes, e-cigarettes, or vapes. See id., at 10; K. Lichtenberg, E-Cigarettes: Current Evidence and Policy, 114 Mo. Med. 335 (2017). Practically overnight, e-cigarettes became ubiquitous. Sales for e-cigarette prod- ucts “surged exponentially” after 2010, 2016 Surgeon Gener- al's Report 152, and according to one estimate, 11.2 million American adults used e-cigarettes by 2016, see O. Obisesan et al., Trends in E-Cigarette Use in Adults in the United Page Proof Pending Publication States, 2016–2018, 180 JAMA Internal Med. 1394 (2020). The impetus for the invention of e-cigarettes was the de- sire to create a product that would reduce the health risks of smoking. A traditional combustible cigarette contains shredded tobacco wrapped in paper, and when lit, the tobacco “catches fre” and “produces smoke, which contains nicotine” and “tar”—a “complex chemical mixture of more than 7,000 compounds that cause a wide range of diseases.” Brief for Global Action To End Smoking, Inc., as Amicus Curiae 14 (internal quotation marks omitted). In contrast, an e- cigarette contains a battery, a heating element or atomizer, a liquid nicotine reservoir, and a mouthpiece. See 2016 Sur- geon General's Report 11. When an e-cigarette user inhales through the device's mouthpiece, the heating coil engages, and the liquid (called e-liquid or e-juice) turns into a nicotine- infused vapor. See ibid. Unlike a traditional cigarette, an e-cigarette does not release tar or other “byproducts of com- bustion,” but it does “emit potentially toxic substances,” in- cluding “fne particulate matter,” “metals,” and, of course, 554 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court nicotine. Brief for Global Action To End Smoking, Inc., as Amicus Curiae 15–16 (internal quotation marks omitted). E-cigarettes typically come in either a “closed” or “open” system. See 2016 Surgeon General's Report 151–152. Closed-system e-cigarettes contain a set amount of e-liquid that is determined by the manufacturer. Some closed- system products are designed to be discarded after the e- liquid supply runs out, while others can be reused by insert- ing a cartridge or pod that contains e-liquid. By contrast, an open-system e-cigarette contains a “tank” that users can manually refll with the desired amount of e-liquid. Users of open-system products may mix their own e-liquids and adjust the amount of e-liquid in the tank. There is ferce public debate about the potential benefts and harms of e-cigarettes. On one hand, many view e- cigarettes as a harm-reduction tool. They enable current smokers who are addicted to nicotine to reduce exposure to Page Proof Pending Publication some of the more harmful byproducts of traditional combus- tible cigarettes. See id., at 10–11; National Academies of Sciences, Engineering, and Medicine, Committee on the Re- view of the Health Effects of Electronic Nicotine Delivery Systems, Public Health Consequences of E-Cigarettes 18 (2018). On the other hand, e-cigarettes, as noted, pose their own health risks, and there is concern that the use of e- cigarettes by non-smokers—and especially young non- smokers—may eventually lead them to smoke conventional cigarettes. See id., at 532–535. Early on, evidence began to mount that young Americans are particularly drawn to e-cigarette products. By the mid- 2010s, approximately 2.4 million high-school students and 620,000 middle-school students reported using an e-cigarette at least once in the last 30 days. 2016 Surgeon General's Report 5, 10. And a more recent estimate suggests that approximately 3.6 million American middle- and high-school students used an e-cigarette within a 30-day period. See Cite as: 604 U. S. 542 (2025) 555 Opinion of the Court Congressional Research Service, H. Sheikh & V. Green, FDA Regulation of Tobacco Products 1 (2021). One particular feature of e-cigarette products appears to drive this youth demand: the panoply of e-liquid favors. One nearly decade-old estimate found that there were 7,700 unique e-liquid favors, including not only favors that were familiar to cigarette smokers (tobacco and menthol) but also fruit, candy, and dessert favors that were appealing to non- smokers. See 2016 Surgeon General's Report 11. The ka- leidoscope of favor options adds to the allure of e-cigarettes and has thus contributed to the booming demand for such products among young Americans. See ibid. Because the popularity of e-cigarettes is a relatively recent phenomenon, these products initially escaped the FDA's reg- ulatory reach. But in 2016, the FDA issued a rule deeming e-cigarettes and e-liquids to be “tobacco products.” 81 Fed. Reg. 29028 (2016). Since most e-cigarette products were Page Proof Pending Publication “not commercially marketed in the United States as of Feb- ruary 15, 2007,” the deeming rule retroactively rendered such products “new tobacco products” subject to the TCA's premarket-authorization regime. 21 U. S. C. § 387j(a)(1)(A). And because those products had not received premarket au- thorization, the effect of the rule was to make their contin- ued sale illegal. Companies that proceeded to sell their products without such authorization would be subject to stiff penalties. See §§ 331(a), 333(a)(1), and (f)(9). To give these manufacturers adequate time to apply for “premarket” authorization, the FDA delayed enforcement for two to three years. See 81 Fed. Reg. 28977–28978. This per- mitted e-cigarette products to remain on the market while manufacturers fled their applications. Initially, applications were due by August 8, 2018. See Vapor Tech. Assn. v. FDA, 977 F. 3d 496, 498 (CA6 2020) (per curiam) (citing 81 Fed. Reg. 29010–29011). The FDA later tried via guidance to extend the compliance deadline through 2022, but a Federal District 556 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court Court ultimately imposed a deadline of September 9, 2020, adding to the time crunch for compliance. See American Academy of Pediatrics v. FDA, 399 F. Supp. 3d 479, 487 (Md. 2019) (imposing a May 12, 2020, deadline); Order in Ameri- can Academy of Pediatrics v. FDA, No. 18–cv–883 (D Md., Apr. 22, 2020), ECF Doc. 182, p. 1 (extending the deadline to September 9, 2020, due to the COVID–19 pandemic); see also Vapor Tech. Assn., 977 F. 3d, at 498–500 (detailing the shift- ing compliance deadline). C At the center of this case are the FDA's actions leading up to its adjudication of manufacturers' premarket tobacco product applications. The agency proposed a rule outlining application requirements, issued guidance to assist e- cigarette manufacturers, and crafted internal memoranda discussing how applications were to be reviewed. These vo- luminous and discursive documents paint a picture of an Page Proof Pending Publication agency that was feeling its way toward a fnal stance and was unable or unwilling to say in clear and specifc terms precisely what applicants would have to provide. Pervading these documents are four overarching topics that animate the dispute before us. 1 The frst topic was the types of scientifc evidence needed to show that an e-cigarette product is “appropriate for the protection of the public health.” § 387j(c)(2)(A). Recall that the TCA states that “well-controlled investigations” may support such a showing “when appropriate, ” § 387j(c)(5)(A), as can “other `valid scientifc evidence' if found suffcient to evaluate the tobacco product,” App. 28 (quoting § 387j(c)(5)(B)). At an October 23, 2018, public meeting, an FDA offcial opined that “[i]n most situations,” the FDA would expect “some analytical testing specifc to [a manufacturer's] product.” FDA/Center for Tobacco Prod- ucts, Tobacco Product Application Review, A Public Meet- Cite as: 604 U. S. 542 (2025) 557 Opinion of the Court ing October 22–23, 2018—Day 2, Sess. 7, Part 2, at 2:12:35– 2:12:43, https://www.fda.gov/tobacco-products/ctp-newsroom/ tobacco-product-application-review-public-meeting#Video2 (2018 Presentation Video). But the FDA also assured man- ufacturers that no “specifc studies,” “[y]outh behavioral data,” or “new nonclinical or clinical studies” would be re- quired. FDA, Premarket Tobacco Product Application Con- tent Overview 18, 26 (Oct. 23, 2018), https://www.fda.gov/ media/117507/download (2018 Presentation). The FDA said much the same thing in a lengthy 2019 guidance document, noting that the “relatively new entrance” of e-cigarette prod- ucts meant that “limited data may exist from scientifc stud- ies and analyses.” App. 28. So, according to this docu- ment, the FDA would not require “long-term studies,” and manufacturers could instead rely on various alternatives, like observational studies, literature reviews, or evidence bridging their new tobacco product to “a studied tobacco Page Proof Pending Publication product.” Id., at 28, 99–105. After manufacturers submitted millions of applications for favored e-cigarette products, the FDA “develop[ed] a new plan to effectively manage” the scientifc evidence underly- ing the onslaught of applications. Id., at 242. In a July 9, 2021, internal memorandum, the FDA took a far less capa- cious view of the scientifc evidence it would consider. Spe- cifcally, the FDA said that it would consider it a “fatal faw” if an application lacked scientifc evidence about a product based on either a randomized controlled trial or a longitu- dinal cohort study. Id., at 243. A “fatal faw” would lead to a manufacturer's “likely receiv[ing] a marketing denial order” for that product. Ibid. Over a month later on August 17, 2021, the FDA issued another internal memorandum that differed in some respects from the July memorandum. It stated that, in addition to randomized controlled trials and longitudinal cohort studies, the FDA “would also consider evidence from another study design, provided that it could reliably and robustly assess 558 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court behavior change” and “compar[e] users of favored products with those of tobacco-favored products.” Id., at 247, n. ix. Then, on August 25, 2021, just before denying respondents' applications, the FDA rescinded the August 17, 2021, memo- randum and stated it would “not consider or rely” on it when evaluating premarket tobacco product applications. Id., at 282. 2 The second topic was the need for manufacturers to com- pare their proposed products to other products. The TCA requires premarket tobacco product applications to provide “full reports of all information . . . concerning investigations which have been made to show” that a new product “pre- sents less risk than other tobacco products.” 21 U. S. C. § 387j(b)(1)(A). Elaborating on that standard at a presenta- tion on October 23, 2018, an FDA offcial encouraged appli- cants to provide comparisons between their products and a Page Proof Pending Publication “representative sample of tobacco products on the market.” 2018 Presentation 11. And a 2019 guidance document simi- larly recommended comparisons of “the health risks of [a manufacturer's] product to both products within the same category and subcategory, as well as products in different categories as appropriate.” App. 30. The 2019 guidance also gave manufacturers discretion to choose comparator products as long as the FDA could “understand [an] appli- cant's rationale and justifcation for [the] comparators chosen.” Ibid. Later that year at a public meeting, an FDA offcial of- fered the same general advice that a successful premarket to- bacco product application “may include comparisons to other tobacco products in the same category or in other categories or subcategories.” FDA/CTP, Deemed Tobacco Product Applications, Video Presentation of Premarket Tobacco Product Applications (PMTAs) Review Process and Re- sources (Oct. 28, 2019), at 31:10–31:16, https://collaboration .fda.gov/ptf 21jryjxyk/?OWASP_CSRFTOKEN=7a8d148 ac776ca8f 3aec38aff7dee12ea4988c1caed05010cded06ab7496 714f. Cite as: 604 U. S. 542 (2025) 559 Opinion of the Court 3 In a lengthy April 2020 guidance document,2 the FDA elaborated on a third theme: its enforcement priorities based on device type. The agency said it would “prioritize en- forcement of favored, cartridge-based” e-cigarette products “other than tobacco- and menthol-favored products.” App. 160. It claimed that “youth overwhelmingly prefer cartridge-based” products, which are “easy to conceal, can be used discreetly, may have a high nicotine content, and are manufactured on a large scale.” Id., at 163. And the document asserted that certain favors, such as candy and fruit favors, “are a strong driver for youth use.” Id., at 164; see also id., at 190 (discussing the increased use of “fruit- and candy-favored” products). Although the FDA sug- gested that its focus on favored, cartridge-based products “should have minimal impact on small manufacturers (e. g., vape shops) that primarily sell non-cartridge-based” prod- Page Proof Pending Publication ucts, it noted that it would also prioritize enforcement against “[a]ll other [e-cigarette] products for which the manu- facturer has failed to take (or is failing to take) adequate measures to prevent minors' access,” as well as “[a]ny [e- cigarette] product that is targeted to minors or whose mar- keting is likely to promote use of [e-cigarettes] by minors.” Id., at 160–161. 4 The fnal theme cutting across these documents is the FDA's unfinching advice that manufacturers should submit “marketing plans” as part of their applications. “Marketing plans” broadly refer to a manufacturer's “specifc restrictions on sale and distribution” that could, for example, “decreas[e] 2 The Fifth Circuit suggested that the FDA's 2020 guidance does not apply here because respondents manufacture “bottles of favored nicotine liquids,” not e-cigarette products themselves. 90 F. 4th 357, 369 (2024) (en banc). But the 2020 guidance concerned the FDA's enforcement prior- ities with respect to “[e]lectronic nicotine delivery systems” or “ENDS,” and, as the guidance document explains, “[e]-liquids are a type of ENDS product.” App. 143 (emphasis deleted). 560 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court the likelihood that those who do not use tobacco products will start using tobacco products.” Id., at 27. In its 2019 guidance, the FDA urged manufacturers to “shar[e]” their “marketing plan[s] to enable FDA to better understand the potential consumer demographic” of their products. Id., at 83. The 2020 enforcement guidance hit the same note, sug- gesting the FDA “intend[ed] to consider” marketing plans and that such plans would be relevant to the agency's en- forcement “prioritization.” Id., at 167, 169. The FDA even offered examples of what marketing restrictions manufac- turers might consider, including screening retailers, age- verifcation technology, mystery-shopper programs, controls over distributors, and quantity limits. Id., at 167–169, 223. It also cautioned that, based on its experience, “focusing on how the product was sold” and “age verifcation” “would not be suffcient to address youth use.” Id., at 215, 220–221. D Page Proof Pending Publication In 2019, the FDA proposed a rule setting out the require- ments for premarket tobacco product applications. See 84 Fed. Reg. 50566 (2019). That proposed rule, in signifcant part, crystallized the four themes discussed above. It of- fered specifcs on the “types of [scientifc] investigations” that applications “would be required to contain.” Id., at 50603; see, e. g., ibid. (listing “[c]ross sectional and longitudi- nal surveys,” “epidemiologic studies,” and “analytic studies” like “randomized controlled clinical trials, cohort studies, and case control studies”); id., at 50599 (proposing “health risk investigations” besides new clinical studies). The proposed rule also required certain cross-product comparisons. See id., at 50603 (requiring that applicants “submit investigations that have been made to show whether the tobacco product has the same or different potential health risks . . . than other tobacco products”). And it underscored the importance of device type with respect to product testing. See id., at 50585 (proposing requirements for constituent testing spe- Cite as: 604 U. S. 542 (2025) 561 Opinion of the Court cifc to open-system products). In addition, the proposed rule obligated manufacturers to submit marketing plans, which were described as “provid[ing] input that is critical” to the agency's review. Id., at 50580, 50581. Notice-and-comment rulemaking takes time, and with a court-imposed deadline fast approaching, the FDA pro- ceeded to adjudicate the frst major wave of premarket to- bacco product applications in August and September 2021 without a fnal rule and the standards it included. It was not until October 5, 2021, that the FDA adopted the fnal rule. See 86 Fed. Reg. 55300 (2021). 1 Respondents Wages and White Lion Investments, LLC, doing business as Triton Distribution, and Vapetasia, LLC, manufacture favored e-liquids for open-system e-cigarettes. Their e-liquid favor offerings include “Killer Kustard Blue- Page Proof Pending Publication berry,” “Rainbow Road,” “Iced Blackberry Lemonade,” “Pineapple Express,” “Suicide Bunny Mother's Milk and Cookies,” and “Blueberry Parfait.” See App. 396, 546, 587, 593, 605, 608. Respondents submitted premarket tobacco product appli- cations on September 9, 2020, the fnal court-ordered dead- line. As the FDA recommended in its guidance, their appli- cations included marketing plans, which touted respondents' use of third-party age-verifcation technology, quantity lim- its, and requirements for retailers to develop compliance checks. See id., at 431–436, 441. To show the safety of their products, respondents “pool[ed] resources” with “other, similarly situated e-liquid companies” to “fund the develop- ment of certain, required non-product specifc data,” includ- ing what they characterized as a “comprehensive review of the scientifc literature.” Id., at 311. One of the respond- ents, Vapetasia, also submitted the results of a cross- sectional survey of current and former adult e-cigarette smokers. See App. to Pet. for Cert. 280a. 562 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court The FDA received applications from more than 500 compa- nies in total, covering more than 6.5 million e-cigarette prod- ucts. See FDA Denies Marketing Applications for About 55,000 Flavored E-Cigarette Products for Failing To Provide Evidence They Appropriately Protect Public Health (Aug. 26, 2021), https://fda.gov/news-events/press-announcements/ fda-denies-marketing-applications-about-55000-flavored-e- cigarette-products-failing-provide-evidence. Almost a year after the court-ordered deadline, the FDA adjudicated its frst slate of premarket tobacco product applications and is- sued marketing denial orders to three manufacturers whose applications covered 55,000 favored e-cigarette products. See ibid. The FDA concluded that the manufacturers failed to provide “suffcient product-specifc scientifc evidence to demonstrate enough of a beneft to adult smokers that would overcome the risk posed to youth.” Ibid. Such “scientifc evidence,” the agency said, “would likely be in the form of a Page Proof Pending Publication randomized controlled trial or longitudinal cohort study,” but the FDA promised that it remained open to “other types of evidence” that are “suffciently robust and reliable.” Ibid. Shortly thereafter, the FDA denied respondents' applica- tions. See App. to Pet. for Cert. 166a, 278a. It concluded that respondents had not provided suffcient scientifc evi- dence to demonstrate that the marketing of their products would be appropriate for the protection of public health. See id., at 166a–167a. Specifcally, the FDA held respond- ents had not provided evidence from a randomized controlled trial, longitudinal cohort study, or another “reliabl[e] and ro- bus[t]” method showing that their dessert-, candy-, and fruit- favored products had benefts “over an appropriate compa- rator tobacco-favored” product. Id., at 167a. With such evidence lacking, the FDA deemed respondents' products “misbranded” and “adulterated” under the FDCA. Id., at 168a. To each denial order, the FDA appended a “Technical Proj- ect Lead (TPL) Review.” See id., at 177a, 285a. These Cite as: 604 U. S. 542 (2025) 563 Opinion of the Court lengthy documents have several noteworthy features. To start, they offer a window into the FDA's evolving under- standing of how favor, regardless of e-cigarette device type, drives youth smoking initiation and nicotine addiction. The reviews canvass the scientifc literature on youth e-cigarette use and explain that this literature had led the agency to conclude that favors make e-cigarette smoking “more palat- able for novice youth and young adults” and may “increase nicotine exposure by potentially infuencing the rate of nico- tine absorption.” Id., at 190a, 298a. What is more, the FDA stated, young people are drawn to particular favors, and the FDA anticipated that its crackdown on one type of e-cigarette device would lead youth to fock to a different type of device to continue using a desired favor. See id., at 192a, 300a. Despite the FDA's prior representations about the impor- tance of marketing plans, the reviews stated that, “for the sake of effciency,” the FDA had decided not to evaluate respondents' marketing plans. Id., at 200a–201a, n. xix, Page Proof Pending Publication 308a–309a, n. xix. The FDA acknowledged that it “is theo- retically possible that signifcant mitigation efforts” could decrease the appeal of favored e-cigarettes to a suffcient degree to counterbalance the documented risks of such products, but it found that none of the marketing plans the FDA had seen had managed to do that. Ibid. The FDA estimates that in its frst wave of marketing or- ders, it issued denials to 320 applicants, who sought approval for approximately 1.2 million products. See Tr. of Oral Arg. 33. 2 Respondents petitioned for review in the Fifth Circuit. A motions panel initially granted a stay of their marketing de- nial orders pending review, see 16 F. 4th 1130, 1134 (2021), but a divided merits panel ultimately denied the petitions, see 41 F. 4th 427, 430 (2022). The court then reheard the case en banc, granted respond- ents' petitions for review, and remanded to the FDA. The 564 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court en banc majority held that the FDA had acted arbitrarily and capriciously in denying respondents' applications. In its view, the FDA performed a surprise switch from the re- quirements articulated in the various predecisional docu- ments. 90 F. 4th 357, 362 (2024). The court pointed to sev- eral main examples of this phenomenon, including the FDA's positions on scientifc evidence, cross-favor comparisons, and device type. See, e. g., id., at 376, 377, 384. The court ex- pressed particular concern that the FDA pulled the rug out from under manufacturers by “not even read[ing] the mar- keting plans it previously said were critical.” Id., at 372. Although the FDA's attorneys represented that the agency had reviewed “ `summar[ies]' ” of respondents' marketing plans, the court deemed that representation an illicit post hoc rationalization. Id., at 373. In a footnote, the en banc majority also suggested that the FDA had violated a provision of the TCA's notice-and- Page Proof Pending Publication comment requirements, see 21 U. S. C. §§ 387g(c)–(d), by im- posing a “de facto ban on favored e-cigarettes” through mass adjudicatory denials, 90 F. 4th, at 384, n. 5. Having found that the FDA had erred in these ways, the court rejected the FDA's suggestion that any errors were harmless. Relying heavily on our decision in Calcutt v. FDIC, 598 U. S. 623 (2023) (per curiam), the court suggested that “APA errors are only harmless where the agency would be required to take the same action no matter what. In all other cases,” the court concluded, “an agency cannot avoid remand.” 90 F. 4th, at 390. And, in a brief alternative analysis, the court found that each of the FDA's errors “plainly affected the procedure used” and was prejudicial. Ibid. (internal quotation marks omitted). Judge Haynes, joined by four other judges, dissented. See ibid. Judge Graves joined the dissent in part. See id., at 405. The en banc Fifth Circuit's decision conficted with those of other Circuits, and we granted the FDA's petition for a Cite as: 604 U. S. 542 (2025) 565 Opinion of the Court writ of certiorari. 603 U. S. 904 (2024). We now vacate and remand. II The question we agreed to decide is whether the FDA acted arbitrarily and capriciously in denying respondents' applications for premarket approval of their tobacco prod- ucts. See Pet. for Cert. I. But before tackling that ques- tion, we briefy address as a preliminary matter an argument that is touched on in respondents' brief: namely, that either the APA or the TCA required the FDA to use notice-and- comment rulemaking to set out the requirements that must be met in a premarket tobacco product application. Unless Congress has specifed otherwise, agencies are gen- erally free to develop regulatory standards “either by gen- eral [legislative] rule or by individual order” in an adjudica- tion. SEC v. Chenery Corp., 332 U. S. 194, 202–203 (1947) (Chenery II). Of course, if a statute requires rulemaking, the affected agency must comply. Ibid. And that is what Page Proof Pending Publication respondents claim in passing here. Respondents' defense of the decision below is based almost entirely on 5 U. S. C. § 706(2)(A) and related case law. But their brief also sug- gests that the FDA's decision to issue denials based on stand- ards developed in adjudication violated other provisions of the APA and TCA that, they claim, required notice-and- comment rulemaking. See Brief for Respondents 47–49, and n. 33. This echoes an argument the Court of Appeals made in a short footnote. See 90 F. 4th, at 384, n. 5 (citing 21 U. S. C. §§ 387g(a)(1)(A), (a)(2), (c)–(d)). We did not grant certiorari on that question, and without adequate briefng, it would not be prudent to decide it here. See Anza v. Ideal Steel Supply Corp., 547 U. S. 451, 461 (2006). Accordingly, we do not reach that question and ex- press no view on its merits.3 3 Respondents' amici offer numerous alternative grounds for affrmance. Three of these arguments are based on the Constitution: (1) that the TCA unconstitutionally delegated lawmaking power to the FDA with respect 566 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court III We now turn to the Court of Appeals' holding that the FDA acted arbitrarily and capriciously. That decision was multifaceted, but its analysis boils down to a central concern: it faulted the FDA for allegedly changing the requirements for premarket tobacco product applications between the time of its guidance and the denials of respondents' applications. The feature of our current case law on arbitrary-and- capricious review that addresses that issue is our change-in- position doctrine. Under that doctrine, we must ask whether the FDA changed course and, if it did, whether it offered satisfactory reasons for the change. Analysis of the FDA's position prior to the denials at issue requires a close reading of nuanced statements in a body of guidance docu- ments that evidence the agency's evolving assessment of the relevant issues. Affected parties may have come away with the impression that the agency would apply a less demanding Page Proof Pending Publication standard of proof than is evident in the denial orders the FDA ultimately issued, but in the end, we cannot say that to, among other things, the necessary contents of a premarket tobacco product application, see Brief for Taxpayers Protection Alliance as Ami- cus Curiae 7–8; (2) that the relevant provisions of the TCA are unconstitu- tionally vague, see id., at 6–8; and (3) that respondents were denied due process, see Brief for Washington Legal Foundation as Amicus Curiae 8– 11; Brief for Thirteen Members of Congress et al. as Amici Curiae 13– 16. Some amici also argue that the FDA violated our “major questions” doctrine. See, e. g., Brief for Vaping Industry Stakeholders as Amici Cu- riae 30–34; Brief for Thirteen Members of Congress et al. as Amici Cu- riae 6–13. Although these issues have a bearing on what appears to have been the Court of Appeals' animating concern—i. e., that the FDA did not give respondents and other applicants fair and accurate notice regarding what it would insist that an application contain—these arguments fall outside the scope of the question presented, were not passed on below, and were not pressed in respondents' brief. We therefore decline to reach them. See, e. g., Atlantic Marine Constr. Co. v. United States Dist. Court for Western Dist. of Tex., 571 U. S. 49, 61 (2013). And our opinion should not be read to suggest any view on their merits. Cite as: 604 U. S. 542 (2025) 567 Opinion of the Court the FDA improperly changed its position with respect to sci- entifc evidence, comparative effcacy, or device type. With respect to the FDA's guidance on marketing plans, we clarify the appropriate legal standard governing claims of harmless error, and we remand to the Fifth Circuit to apply that standard in the frst instance. A We begin with our change-in-position doctrine. The APA requires a reviewing court to “hold unlawful and set aside agency action” found to be “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” 5 U. S. C. § 706(2)(A). Our well-worn arbitrary-and-capricious standard ensures that an administrative agency “examine[d] the relevant data and articulate[d] a satisfactory explanation for its action including a rational connection between the facts found and the choice made.” Motor Vehicle Mfrs. Page Proof Pending Publication Assn. of United States, Inc. v. State Farm Mut. Automobile Ins. Co., 463 U. S. 29, 43 (1983) (internal quotation marks omitted). The scope of this review “is narrow,” and review- ing courts must exercise appropriate deference to agency de- cisionmaking and not substitute their own judgment for that of the agency. Ibid. Our case law identifes numerous ways in which an agency may act arbitrarily and capriciously. The Fifth Circuit con- cluded that the FDA overstepped this standard in four such ways. In its view, the FDA (1) “invent[ed] post hoc justif- cations” for its failure to consider applicants' marketing plans; (2) failed to give “fair notice” of the evidentiary and comparative requirements that would be imposed at the ap- plication stage; (3) changed its position regarding scientifc evidence and device type; and (4) faulted respondent “for re- lying in good faith on [its] previous” guidance. 90 F. 4th, at 371–386. All four of these principles orbit around the same basic concern: an agency should not mislead regulated entities. 568 FDA v. WAGES AND WHITE LION INVESTMENTS, LLC Opinion of the Court The essence of respondents' argument is that the FDA told them in guidance documents that it would do one thing and then turned around and did something different when it re- viewed their applications. The change-in-position doctrine is administrative law's an- swer to that problem. Under that doctrine, “[a]gencies are free to change their existing policies as long as they provide a reasoned explanation for the change,” “ `display awareness that [they are] changing position,' ” and consider “ `serious reliance interests.' ” Encino Motorcars, LLC v. Navarro, 579 U. S. 211, 221–222 (2016) (quoting FCC v. Fox Television Stations, Inc., 556 U. S. 502, 515 (2009)). For reasons