Full opinion text
Per Curiam: In October 2017, a lone gunman armed with bump-stock-enhanced semiautomatic weapons murdered 58 people and wounded hundreds more in a mass shooting at a concert in Las Vegas, Nevada. In the wake of that tragedy, the Bureau of Alcohol, Tobacco, Firearms and Explosives ("Bureau") promulgated through formal notice-and-comment proceedings a rule that classifies bump-stock devices as machine guns under the National Firearms Act, 26 U.S.C. §§ 5801 - 5872. See Bump-Stock-Type Devices, 83 Fed. Reg. 66,514 (Dec. 26, 2018) ("Bump-Stock Rule"). The then-Acting Attorney General Matthew Whitaker initially signed the final Bump-Stock Rule, and Attorney General William Barr independently ratified it shortly after taking office. Bump-stock owners and advocates filed separate lawsuits in the United States District Court for the District of Columbia to prevent the Rule from taking effect. The district court denied the plaintiffs' motions for a preliminary injunction to halt the Rule's effective date. Guedes v. Bureau of Alcohol, Tobacco, Firearms, and Explosives , 356 F.Supp.3d 109 (D.D.C. 2019). We affirm the denial of preliminary injunctive relief. I A The National Firearms Act (i) regulates the production, dealing in, possession, transfer, import, and export of covered firearms; (ii) creates a national firearms registry; and (iii) imposes taxes on firearms importers, manufacturers, and dealers, as well as specified transfers of covered firearms. 26 U.S.C. §§ 5801 - 5861. Failure to comply with the National Firearms Act's requirements results in penalties and forfeiture, and subjects the violator to the general enforcement measures available under the internal revenue laws. Id . §§ 5871-5872. The firearms subject to regulation and registration under the National Firearms Act include "machinegun[s]." 26 U.S.C. § 5845(a). The statute defines a "machinegun" as "any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger." 26 U.S.C. § 5845(b). The definition also covers "the frame or receiver of any such weapon," as well as "any part" or "combination of parts designed and intended, for use in converting a weapon into a machinegun," and "any combination of parts from which a machinegun can be assembled" as long as those "parts are in the possession or under the control of a person." Id . Congress expressly charged the Attorney General with the "administration and enforcement" of the National Firearms Act, 26 U.S.C. § 7801(a)(1), (a)(2)(A), and provided that the Attorney General "shall prescribe all needful rules and regulations for the enforcement of" the Act," id . § 7805; see id . § 7801(a)(2)(A). The Gun Control Act of 1968, 18 U.S.C. § 921 et seq ., as amended by the Firearm Owners' Protection Act, Pub. L. No. 99-308, 100 Stat. 449 (1986), imposes both a regulatory licensing scheme and criminal prohibitions on specified firearms transactions. See 18 U.S.C. § 923 (licensing scheme); id . § 922 (criminal prohibitions). The Gun Control Act incorporates by reference the definition of machine gun in the National Firearms Act, 26 U.S.C. § 5845(b). See 18 U.S.C. § 921(a)(23). The Gun Control Act also expressly delegates administrative and rulemaking authority to the Attorney General to "prescribe only such rules and regulations as are necessary to carry out the provisions of this chapter." Id . § 926(a). The Attorney General has delegated the responsibility for administering and enforcing the National Firearms Act and the Gun Control Act to the Bureau. See 28 C.F.R. § 0.130(a). B 1 Machine guns are generally prohibited by federal law. See 18 U.S.C. § 922(o). On the other hand, many firearms that require a distinct pull of the trigger to shoot each bullet are lawful. See generally id. § 922 ; 26 U.S.C. § 5845. A "bump stock" is a device that replaces the standard stationary stock of a semiautomatic rifle-the part of the rifle that typically rests against the shooter's shoulder-with a non-stationary, sliding stock that allows the shooter to rapidly increase the rate of fire, approximating that of an automatic weapon. 83 Fed. Reg. at 66,516. A bump stock does so by channeling and directing the recoil energy from each shot "into the space created by the sliding stock (approximately 1.5 inches) in constrained linear rearward and forward paths." Id . at 66,518. In so doing, the bump stock "harnesses the firearm's recoil energy as part of a continuous back-and-forth cycle that allows the shooter to attain continuous firing" following a single pull of the trigger. Id. at 66,533. That design allows the shooter, by maintaining constant backward pressure on the trigger as well as forward pressure on the front of the gun, to fire bullets continuously and at a high rate of fire to "mimic" the performance of a fully automatic weapon. Id . at 66,516. Exercising his regulatory authority, the Attorney General first included a bump-stock type device within the statutory definition of "machinegun" in 2006. See ATF Ruling 2006-2; see also Akins v. United States , 312 F. App'x 197, 199 (11th Cir. 2009) (summary order). In later years, some other bumpstock devices were not categorized as machine guns. 83 Fed. Reg. at 66,514. 2 On October 1, 2017, a shooter used multiple semiautomatic rifles equipped with bump stocks to fire several hundred rounds of ammunition into a crowd of concert attendees within a roughly ten-minute span of time. The " 'rapid fire' operation" of the shooter's weapons enabled by the bump stocks left 58 dead and approximately 500 wounded. 83 Fed. Reg. at 66,516. The Las Vegas massacre prompted an immediate outcry from the public and members of Congress. See Guedes , 356 F.Supp.3d at 120, 123. In response, President Trump "direct[ed] the Department of Justice, * * * as expeditiously as possible, to propose for notice and comment a rule banning all devices that turn legal weapons into machineguns." Application of the Definition of Machinegun to "Bump Fire" Stocks and Other Similar Devices, 83 Fed. Reg. 7,949, 7,949 (Feb. 20, 2018). The Bureau then revisited the status of bump stocks and addressed the variation in its prior positions. 83 Fed. Reg. at 66,516-66,517. On March 29, 2018, then-Attorney General Sessions issued a Notice of Proposed Rulemaking that suggested "amend[ing] the Bureau of Alcohol, Tobacco, Firearms, and Explosives regulations to clarify that [bumpstock-type devices] are 'machineguns' " under 26 U.S.C. § 5845(b). See Bump-Stock-Type Devices, 83 Fed. Reg. 13,442 (March 29, 2018). The Bureau promulgated its final rule on December 26, 2018. With respect to the statutory definition of machine gun, the Bump-Stock Rule provided that the National Firearms Act's use of "the term 'automatically' as it modifies 'shoots, is designed to shoot, or can be readily restored to shoot,' " 26 U.S.C. § 5845(b), "means functioning as the result of a self-acting or self-regulating mechanism that allows the firing of multiple rounds through a single function of the trigger." 83 Fed. Reg. at 66,553-66,554 (codified at 27 C.F.R. §§ 447.11, 478.11, 479.11 ). The Rule further defined "single function of the trigger," 26 U.S.C. § 5845(b), to mean "a single pull of the trigger and analogous motions." 83 Fed. Reg. at 66,553-66,554 (codified at 27 C.F.R. §§ 447.11, 478.11, 479.11 ). In light of those definitions, the Bump-Stock Rule concluded that the statutory term " 'machinegun' includes a bump-stock-type device"-that is, "a device that allows a semiautomatic firearm to shoot more than one shot with a single pull of the trigger by harnessing the recoil energy of the semiautomatic firearm to which it is affixed so that the trigger resets and continues firing without additional physical manipulation of the trigger by the shooter." 83 Fed. Reg. at 66,553-66,554 (codified at 27 C.F.R. §§ 447.11, 478.11, 479.11 ). In adopting the Bump-Stock Rule, the Bureau relied on both the "plain meaning" of the statute and the agency's charge to implement the National Firearms Act and the Gun Control Act. 83 Fed. Reg. at 66,527 (citing and invoking Chevron, U.S.A. v. Natural Res. Def. Council , 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984) ). The Bureau explained that the Bump-Stock Rule both "accord[s] with the plain meaning" of the statute, and "rests on a reasonable construction of" any "ambiguous" statutory terms. Id. In the Bureau's view, by not further defining the terms "automatically" and "single function of the trigger," Congress "left it to the [Attorney General] to define [them] in the event those terms are ambiguous." Id . (citing Chevron , 467 U.S. at 844, 104 S.Ct. 2778 ); see also id . at 66,515 (citing delegations of regulatory authority under 26 U.S.C. §§ 7801(a)(2)(A), 7805(a), and 18 U.S.C. § 926(a) ). The Bureau was explicit that the Bump-Stock Rule would only become "effective" on March 26, 2019, ninety days after promulgation. 83 Fed. Reg. at 66,514. The Bureau further assured that individuals would be subject to "criminal liability only for possessing bump-stock-type devices af ter the effective date of regulation, not for possession before that date." Id . at 66,525; see also id . (providing that the Rule "criminalize[s] only future conduct, not past possession of bump-stock-type devices that ceases by the effective date"); id . at 66,539 ("To the extent that owners timely destroy or abandon these bumpstock-type devices, they will not be in violation of the law[.]"). Bump-stock owners were directed to destroy their devices or leave them at a Bureau office by March 26, 2019. Id. at 66,514. Although most of the rulemaking process occurred during the tenure of Attorney General Jefferson Sessions, he resigned his office on November 7, 2018. The President then invoked the Federal Vacancies Reform Act of 1998 ("Reform Act"), 5 U.S.C. § 3345(a)(3), to designate Matthew Whitaker, who had been Sessions' chief of staff, "to perform the functions and duties of the office of Attorney General, until the position is filled by appointment or subsequent designation." Memorandum from President Donald Trump to Matthew George Whitaker, Chief of Staff, Department of Justice (Nov. 8, 2018), J.A. 277. The final Bump-Stock Rule was signed by then-Acting Attorney General Whitaker. Whitaker served as the Acting Attorney General for 98 days, until William Barr was sworn in as the Attorney General on February 14, 2019. See Bump-Stock-Type Devices, 84 Fed. Reg. 9,239, 9,240 (March 14, 2019). On March 11, 2019, Attorney General Barr announced that he had "independently reevaluate[d]" the Bump-Stock Rule and the "underlying rulemaking record." 94 Fed. Reg. at 9,240. "[H]aving reevaluated those materials without any deference to [Whitaker's] earlier decision," Attorney General Barr "personally c[a]me to the conclusion that it is appropriate to ratify and affirm the final rule," and did so. Id. C Three groups of bump-stock owners and advocates filed suit in the United States District Court for the District of Columbia to prevent the Bump-Stock Rule from taking effect. See Damien Guedes v. Bureau of Alcohol, Tobacco, Firearms, and Explosives , No. 18-cv-2988; David Codrea v. William P. Barr , No. 18-cv-3086; Firearms Policy Coalition, Inc. v. William P. Barr , No. 18-cv-3083. As relevant here, the Guedes plaintiffs ("Guedes") and the Codrea plaintiffs ("Codrea") argued that the Bureau promulgated the Bump-Stock Rule in violation of the Administrative Procedure Act, 5 U.S.C. § 500 et seq . Also, the Firearms Policy Coalition ("Coalition") and Codrea argued that Acting Attorney General Whitaker lacked the legal authority to promulgate the Rule because his designation as Acting Attorney General violated the Attorney General Act, 28 U.S.C. § 508, and the Appointments Clause of the Constitution, Article II, Section 2, Clause 2. The district court denied all three motions for a preliminary injunction. Guedes , 356 F.Supp.3d at 119. The district court concluded that Guedes, Codrea, and the Coalition had not demonstrated a likelihood of success on the merits. The court first held that "[m]ost of the plaintiffs' administrative law challenges are foreclosed by the Chevron doctrine," and the Rule "adequately explained" the agency's decision to classify bump-stock-type devices as machine guns. Id . at 120. As to the challenges to Whitaker's authority, the district court held that the Reform Act permits the President to deviate from the line of succession that the Attorney General Act provides, subject to certain statutory limitations that indisputably were satisfied with Whitaker's appointment. Guedes , 356 F.Supp.3d at 120-121. The court also rejected the Coalition's and Codrea's Appointments Clause challenge as "foreclosed by Supreme Court precedent and historical practice." Id . at 121. Guedes, Codrea, and the Coalition all appealed. But none of them sought a stay or an injunction pending appeal. They chose instead to seek highly expedited disposition, which this court granted. While the appeal was pending, Attorney General Barr ratified and individually endorsed the final Bump-Stock Rule. At the post-argument request of the Coalition, we voluntarily dismissed its appeal. Order, Guedes v. Bureau of Alcohol, Tobacco, Firearms, and Explosives , No. 19-5042, 2019 WL 1398194 (March 23, 2019) (per curiam). But because Codrea presses the same challenge to Whitaker's authority to promulgate the Rule as the Coalition had raised, Codrea Br. 20-21, that issue remains before us in reviewing the district court's denial of a preliminary injunction. II A preliminary injunction is "an extraordinary remedy that may only be awarded upon a clear showing that the plaintiff is entitled to such relief." Winter v. Natural Res. Def. Council, Inc. , 555 U.S. 7, 22, 129 S.Ct. 365, 172 L.Ed.2d 249 (2008). The plaintiffs bear the burden of persuasion in seeking preliminary relief. Cobell v. Norton , 391 F.3d 251, 258 (D.C. Cir. 2004). Specifically, Guedes and Codrea must establish that: (1) they are "likely to succeed on the merits"; (2) they are "likely to suffer irreparable harm in the absence of preliminary relief"; (3) the "balance of equities" tips in their favor; and (4) "an injunction is in the public interest." Winter , 555 U.S. at 20, 129 S.Ct. 365 ; accord Aamer v. Obama , 742 F.3d 1023, 1038 (D.C. Cir. 2014). The last two factors "merge when the Government is the opposing party." Nken v. Holder , 556 U.S. 418, 435, 129 S.Ct. 1749, 173 L.Ed.2d 550 (2009). We review a district court's denial of a preliminary injunction for an abuse of discretion, but in doing so we review the district court's legal conclusions de novo and any findings of fact for clear error. Serono Labs., Inc. v. Shalala , 158 F.3d 1313, 1318 (D.C. Cir. 1998). III A foundational requirement for obtaining preliminary injunctive relief is that the plaintiffs demonstrate a likelihood of success on the merits. See Nken , 556 U.S. at 434, 129 S.Ct. 1749 ("The first two factors of the traditional standard [i.e. , likelihood of success on the merits and irreparable injury] are the most critical."); Sherley v. Sebelius , 644 F.3d 388, 393 (D.C. Cir. 2011) (raising the possibility that "likelihood of success is an independent, free-standing requirement for a preliminary injunction") (quoting Davis v. Pension Benefit Guar. Corp. , 571 F.3d 1288, 1296 (D.C. Cir. 2009) (Kavanaugh, J., concurring)). Neither the challenge to Acting Attorney General Whitaker's authority nor the objections to the substantive validity of the Bump-Stock Rule clears that hurdle. And because the plaintiffs have shown no likelihood of success on the merits, we choose not to "proceed to review the other three preliminary injunction factors." Arkansas Dairy Coop. Ass'nv. United States Dep't of Agric. , 573 F.3d 815, 832 (D.C. Cir. 2009). A Codrea levels a broadside attack on the rule as categorically invalid because Acting Attorney General Whitaker allegedly lacked the legal authority to approve the Bump-Stock Rule's issuance. Specifically, Codrea argues that Whitaker's designation to serve as Acting Attorney General violated both the Attorney General Act, 28 U.S.C. § 508, and the Constitution's Appointments Clause, U.S. Const. Art. II, § 2, cl. 2. Whether or not those arguments would otherwise have had merit (something we do not decide), Codrea has no likelihood of success on this claim because the rule has been independently ratified by Attorney General William Barr, whose valid appointment and authority to ratify is unquestioned. The Appointments Clause requires that "all * * * Officers of the United States" be appointed by the President "by and with the Advice and Consent of the Senate." U.S. Const. Art. II, § 2, cl. 2. This requirement is the "default manner of appointment," Edmond v. United States , 520 U.S. 651, 660, 117 S.Ct. 1573, 137 L.Ed.2d 917 (1997), with the only exception being that Congress may vest the appointment of "inferior Officers" in "the President alone," "Courts of Law," and "the Heads of Departments," U.S. Const. Art. II, § 2, cl. 2. One stark consequence of this scheme is that "the responsibilities of an office * * * [can] go unperformed if a vacancy arises and the President and Senate cannot promptly agree on a replacement." National Labor Relations Bd. v. SW Gen., Inc. , --- U.S. ----, 137 S.Ct. 929, 934, 197 L.Ed.2d 263 (2017) ; Buckley v. Valeo, 424 U.S. 1, 132, 96 S.Ct. 612, 46 L.Ed.2d 659 (1976) (per curiam) ("[A]ll officers of the United States are to be appointed in accordance with the Clause."). "Since the beginning of the nation," Congress has addressed this problem through "vacancy statutes" that grant the President the authority to designate acting officials to "keep the federal bureaucracy humming." SW General, Inc. v. National Labor Relations Bd. , 796 F.3d 67, 70 (D.C. Cir. 2015) (quotation marks omitted), aff'd , --- U.S. ----, 137 S.Ct. 929, 197 L.Ed.2d 263 (2017). The Reform Act is the most recent iteration of that interbranch accommodation. It provides for three options whenever a Senate-confirmed officer "dies, resigns, or is otherwise unable to perform the functions and duties of the office[.]" 5 U.S.C. § 3345(a). The default is for the "first assistant" to take the helm. Id . § 3345(a)(1). But the Reform Act allows the President to choose another person instead, as long as that person is either a Senate-confirmed appointee, id . § 3345(a)(2), or an employee within the same agency, subject to certain duration-of-service and pay-scale requirements, id . § 3345(a)(3). Mr. Whitaker was designated under the latter option, since his service as chief of staff comported with the Reform Act's duration-of-service and pay grade requirements. Guedes , 356 F.Supp.3d at 138 ("The parties do not dispute that Whitaker satisfies the eligibility criteria in the [Reform Act.]"). Congress broadly designated the Reform Act to be the "exclusive means for temporarily authorizing an acting official to perform the functions and duties of any" Executive office that would otherwise require Senate confirmation. 5 U.S.C. § 3347(a). But there is an "unless"-Congress crafted exceptions to that exclusivity. Id . As relevant here, Section 3347(a) does not control if another "statutory provision expressly * * * designates an officer or employee to perform the functions and duties of a specified office temporarily in an acting capacity[.]" Id . § 3347(a)(1)(B). The Attorney General Act, 28 U.S.C. § 508, is one of those office-specific vacancy statutes. That statute specifies a line of succession for a vacancy in the Office of the Attorney General. First in line is the Deputy Attorney General, who "may exercise all the duties of th[e] office" and who, "for the purpose of section 3345 of [the Reform Act]," is deemed "the first assistant to the Attorney General." 28 U.S.C. § 508(a). If the Deputy Attorney General is unavailable, the Attorney General Act directs that "the Associate Attorney General shall act as Attorney General," and "[t]he Attorney General may designate the Solicitor General and the Assistant Attorneys General, in further order of succession, to act as Attorney General." Id. § 508(b). Codrea and the Department have battled at length over the interaction between the Reform Act and the Attorney General Act in the event of a vacancy in the position of the Attorney General. The Government maintains, and the district court agreed, that the two statutes provide the President with alternative means of designating an acting replacement. Guedes , 356 F.Supp.3d at 139 ; Gov't Br. 40-58. Codrea, by comparison, reads the Attorney General Act as the exclusive path for designating an acting Attorney General, with the Reform Act available only after the line of succession in the Attorney General Act has been exhausted. Codrea Br. 20-21 (incorporating Coalition Br. 6). Codrea also argues that the designation of a mere employee to perform the duties of a principal office like that of the Attorney General, even on an acting basis, raises substantial constitutional questions, at least when no exigency requires that designation. Id. (adopting Coalition Reply Br. 15). We need not wade into that thicket. While this appeal was pending, Attorney General Barr independently "familiarized [him]self with the rulemaking record [and] * * * reevaluated those materials without any deference to [Whitaker's] earlier decision." 84 Fed. Reg. at 9,240. Following this "independent[ ] reevaluat[ion] [of] the * * * rule and the underlying rulemaking record," Attorney General Barr "personally c[a]me to the conclusion that it [wa]s appropriate to ratify and affirm the final rule." Id. Codrea accepts the validity of Attorney General Barr's ratification as to both his statutory and his Appointments Clause claims. Codrea Br. 20-21 (adopting Coalition Reply Br. 22); see also 5 U.S.C. § 3348(d)(1)-(2) (only prohibiting the ratification of nondelegable duties); 28 U.S.C. § 510 (authorizing delegation of "any function of the Attorney General"). And with that act of ratification and the concession, Codrea's likelihood of success on the merits of his challenge to the rule based on Acting Attorney General Whitaker's role in its promulgation reduces to zero. Codrea insists otherwise. He argues that Attorney General Barr's ratification does not moot the claim because of the mootness doctrine's exceptions for a defendant's voluntary cessation of challenged conduct or for acts capable of repetition yet evading review. Codrea Br. 20-21 (adopting Coalition Reply Br. 17). That argument fails because ratification is generally treated as a disposition on the legal merits of the appointments challenge and, in any event, no mootness exception applies in this case. 1 The mootness doctrine "ensures compliance with Article III's case and controversy requirement by 'limit[ing] federal courts to deciding actual, ongoing controversies.' " Aref v. Lynch , 833 F.3d 242, 250 (D.C. Cir. 2016) (quoting American Bar Ass'n v. FTC , 636 F.3d 641, 645 (D.C. Cir. 2011) ). A case is moot if our decision will neither "presently affect the parties' rights nor have a more-than-speculative chance of affecting them in the future." Id. (internal quotation marks omitted) (quoting American Bar Ass'n , 636 F.3d at 645 ). We have repeatedly held that a properly appointed official's ratification of an allegedly improper official's prior action, rather than mooting a claim, resolves the claim on the merits by "remedy[ing] [the] defect" (if any) from the initial appointment. Wilkes-Barre Hosp. Co. v. National Labor Relations Bd. , 857 F.3d 364, 371 (D.C. Cir. 2017). This is so regardless of whether "the previous [officer] was" or was not "validly appointed under either the Vacancies Act or the Appointments Clause." Intercollegiate Broad. Sys. Inc. v. Copyright Royalty Bd ., 796 F.3d 111, 119 n.3 (D.C. Cir. 2015) (ratification defeats Appointments Clause challenge) (citing Doolin Sec. Sav. Bank, F.S.B. v. Office of Thrift Supervision , 139 F.3d 203, 205, 207, 212-214 (D.C. Cir. 1998), superseded by statute on other grounds , Federal Vacancies Reform Act of 1998, Pub. L. No. 105-277, 122 Stat. 2681,as recognized in SW Gen., Inc. , 796 F.3d at 70-71 ); FEC v. Legi-Tech, Inc. , 75 F.3d 704, 706, 708-710 (D.C. Cir. 1996) (similar). In Doolin , we treated the curative effects of ratification as analogous to rendering any defect in the agency's action "harmless error" under the Administrative Procedure Act, 5 U.S.C. § 706. 139 F.3d at 212. So viewed, ratification purges any residual taint or prejudice left over from the allegedly invalid appointment. Legi-Tech, 75 F.3d at 708 n.5 ("[T]he issue is not whether Legi -Tech was prejudiced by the original [decision], which it undoubtedly was, but whether, given the FEC's remedial actions, there is sufficient remaining prejudice to warrant dismissal."); Intercollegiate Broad. , 796 F.3d at 124 (citing Legi-Tech for the same proposition). When viewed as analogous to harmless-error analysis, ratification is treated as resolving the merits of the challenger's claim in the agency's favor. Cf. Doolin , 139 F.3d at 212 ; Combat Veterans for Cong. Political Action Comm. v. FEC , 795 F.3d 151, 157 (D.C. Cir. 2015) (rejecting a procedural challenge to a Federal Election Commission fine on the merits because the alleged infirmity produced no "prejudice"). Those cases' treatment of ratification as resolving the merits of a claimed appointment flaw parallels how this court analyzes the agency practice of post-promulgation notice and comment. When an agency "issues final regulations without the requisite comment period and then tries to cure that Administrative Procedure Act violation by holding a post-promulgation comment period," we have repeatedly held that the agency prevails on the merits as long as it can demonstrate that it has kept an "open mind" throughout the subsequent comment period. See , e.g. , Intermountain Ins. Serv. of Vail v. Commissioner, 650 F.3d 691, 709 (D.C. Cir. 2011) (emphasis added), vacated and remanded on other grounds , 566 U.S. 972, 132 S.Ct. 2120, 182 L.Ed.2d 865 (2012), dismissed on unopposed motion , No. 10-1204, 2012 WL 2371486, at *1 (D.C. Cir. June 11, 2012) ; Advocates for Highway & Auto Safety v. Federal Highway Admin., 28 F.3d 1288, 1291-1293 (D.C. Cir. 1994) (same). Codrea points to Landry v. FDIC , 204 F.3d 1125 (D.C. Cir. 2000), in which this court resolved the merits of an Appointments Clause challenge to an administrative law judge's decision, notwithstanding the subsequent de novo review and affirmance of that decision by the agency itself, id. at 1131. That case is of no help to Codrea. Landry carved out a narrow exception to ratification's curative effect for Appointments Clause challenges to the acts of "purely decision recommending employees." Id. at 1131-1132. This court explained that, if ratification were an escape hatch in those cases, "then all such arrangements would escape judicial review" because the challenged ALJ action would never obtain judicial review without first exhausting that ratifying internal agency review process. Id. Only when that particular "catch-22" is present does the Landry approach apply. Id. ; accord Intercollegiate Broad. , 796 F.3d at 124 (distinguishing Landry on that basis). The succession of a Presidentially appointed and Senate-confirmed Attorney General does not remotely implicate the Landry scenario. 2 Codrea argues that we should analyze the effect of ratification through the lens of mootness rather than treating ratification as resolving the case on the merits. Codrea Br. 20-21 (adopting Coalition Reply Br. 16-17). Codrea notes that all of our prior ratification cases dealt with appointments challenges that arose as defenses to enforcement actions that were being prosecuted by a properly appointed official, but that were allegedly "tainted" by some preceding action of an unlawfully appointed official. Codrea Br. 20-21 (adopting Coalition Reply Br. 20); see, e.g. , Intercollegiate Broad. , 796 F.3d at 124 (raising Appointments Clause defense in a "subsequent proceeding" based on the "continuing taint arising from the first" proceeding); Doolin , 139 F.3d at 212 (raising Appointments Clause challenge to officer who issued the initial "Notice of Charges" to collaterally attack the ultimate cease-and-desist order issued by a validly appointed officer). In that scenario, Codrea reasons, the appointment issue arose only as an affirmative defense; no act intervened during litigation to eliminate the factual basis for an affirmative claim for relief in a way that generally would trigger mootness analysis. Here, by contrast, Codrea has raised as a plaintiff an independent, pre-enforcement challenge to an agency rule in an attempt to avert a present duty to comply, and he filed suit at a time when the allegedly improperly appointed official was still in office and enforcing his own challenged decision. For that reason, the effect of Attorney General Barr's intervening ratification must be guided not by a merits analysis, but rather by mootness. Codrea Br. 20-21 (adopting Coalition Reply Br. 17); see, e.g. , EEOC v. First Citizens Bank of Billings , 758 F.2d 397, 399-400 (9th Cir. 1985) (treating congressional ratification as causing mootness); see also Thomas v. Network Solutions, Inc. , 176 F.3d 500, 506 (D.C. Cir. 1999) (assuming that congressional ratification mooted an unauthorized-tax claim). The problem for Codrea is that, even if we were to adopt his proposed analytical approach, his claim still lacks any discernible likelihood of success on the merits because no exception to mootness fits this scenario. First , this case does not implicate the exception to mootness for cases that are "capable of repetition, yet evading review." United States v. Sanchez-Gomez , --- U.S. ----, 138 S.Ct. 1532, 1540, 200 L.Ed.2d 792 (2018). For a controversy to be "capable of repetition," Codrea bears the burden of showing that (i) the challenged action is "in its duration too short to be fully litigated prior to its cessation or expiration," and (ii) there is a "reasonable expectation that the same complaining party will be subject to the same action again." Davis v. FEC , 554 U.S. 724, 735, 128 S.Ct. 2759, 171 L.Ed.2d 737 (2008) (citations omitted); Honeywell Int'l, Inc. v. Nuclear Regulatory Comm'n, 628 F.3d 568, 576 (D.C. Cir. 2010) (party asserting capable of repetition bears burden of proof) (citing Southern Co. Servs., Inc. v. FERC , 416 F.3d 39, 43 (D.C. Cir. 2005) ). Under that test, "[t]he 'wrong' that is, or is not, 'capable of repetition' must be defined in terms of the precise controversy it spawns ." People for Ethical Treatment of Animals, Inc. v. Gittens , 396 F.3d 416, 422 (D.C. Cir. 2005) (emphasis added). This demand for particularity ensures "that courts resolve only continuing controversies between the parties." Id. Here, Codrea has wholly failed to show that appointments claims like his are too short-fused to obtain judicial resolution, or that there is anything more than the most remote and "theoretical[ ] possib[ility]" of repetition, Nelson v. Miller , 570 F.3d 868, 882 (7th Cir. 2009). For Codrea's legal injury to recur, (i) the Attorney General would have to leave office; (ii) the President would then have to appoint a mere employee in his stead (something Codrea argues has not happened more than a "handful" of times in history (Codrea Br. 20-21 (adopting Coalition Br. 38; Coalition Reply Br. 15-16)); (iii) that the new Acting Attorney General would then have to promulgate a legislative rule; and (iv) by sheer coincidence, that rule would have to adversely affect Codrea or his co-plaintiffs' legal rights. It takes more than such quixotic speculation to save a case from mootness, even when the Executive continues to defend its prerogatives in litigation. See Larsen v. United States Navy , 525 F.3d 1, 4 (D.C. Cir. 2008). Second , Codrea's invocation of the rule that a defendant's voluntary cessation of challenged activity will not moot a case fares no better. See Friends of the Earth, Inc. v. Laidlaw Environmental Servs. , 528 U.S. 167, 189, 120 S.Ct. 693, 145 L.Ed.2d 610 (2000). The voluntary-cessation rule is designed to deter the wrongdoer who would otherwise "engage in unlawful conduct, stop when sued to have the case declared moot, then pick up where he left off, repeating this cycle until he achieves all his unlawful ends." Already, LLC v. Nike, Inc. , 568 U.S. 85, 91, 133 S.Ct. 721, 184 L.Ed.2d 553 (2013). For that reason, a party's voluntary cessation of challenged conduct will not moot a case unless it is "absolutely clear that the allegedly wrongful behavior could not reasonably be expected to recur." Laidlaw Environmental Servs. , 528 U.S. at 189, 120 S.Ct. 693 (internal quotation marks omitted). The voluntary-cessation doctrine has no apparent relevance here. That is because the power to effect the legally relevant ratification by a duly installed Attorney General-the supposed source of "cessation"-lies beyond the unilateral legal authority of any of the named defendants, the Office of the Attorney General, or even the President of the United States. Under the peculiar circumstances of this case, where the ratification was a result of the combined actions of a presidential nomination and an independent Senate confirmation, the "voluntariness" in "voluntary cessation" is not implicated. Aimed as it is at party manipulation of the judicial process through the false pretense of singlehandedly ending a dispute, the voluntary-cessation exception presupposes that the infringing party voluntarily exercises its own unilateral power not only to terminate the suit and evade judicial review, but also to "pick up where he left off" and complete the devious "cycle" after the litigation is dismissed. Already, LLC , 568 U.S. at 91, 133 S.Ct. 721 ; see City News & Novelty, Inc. v. City of Waukesha , 531 U.S. 278, 284 n.1, 121 S.Ct. 743, 148 L.Ed.2d 757 (2001) (explaining that the "rule traces to the principle that a party should not be able to evade judicial review, or to defeat a judgment, by temporarily altering questionable behavior") (emphasis added); Knox v. Service Emps. Int'l Union , 567 U.S. 298, 307, 132 S.Ct. 2277, 183 L.Ed.2d 281 (2012) (voluntary cessation concerns a defendant's "resumption of * * * challenged conduct as soon as the case is dismissed") (emphasis added); United States v. W.T. Grant Co. , 345 U.S. 629, 632, 73 S.Ct. 894, 97 L.Ed. 1303 (1953) (voluntary-cessation doctrine rooted in concern over leaving a "defendant * * * free to return to his old ways"). That framework ill fits a situation where, as here, the intervening acts of independent third parties are essential to accomplish a legally relevant change in circumstances. Here, ratification materially changed the circumstances of the litigation only because it was undertaken by a validly appointed Attorney General whose authority to act Codrea does not challenge. Codrea Br. 20-21 (adopting Coalition Reply Br. 22) ("Plaintiff assumes that the ratification was not tainted by Mr. Whitaker's actions in promulgating the Rule in the first place."). That "cessation" of the legal challenge was outside the hands of the named defendants-then-Acting Attorney General Whitaker, the Bureau of Alcohol, Tobacco, Firearms and Explosives, Acting Bureau Director Thomas Brandon, and Attorney General William Barr. The essential predicate for that legally relevant form of cessation was the (non-defendant) President's nomination and the (non-defendant) Senate's independent confirmation of a new Attorney General, and their endowment of him with the authority to "cease" the litigation by way of ratification. In other words, the defendants in this case lacked the unilateral power, or the power at all, to voluntarily cease and restart the conduct complained of-having a Reform-Act-appointed Acting Attorney General promulgate or enforce a rule adversely affecting Guedes and Codrea. Without such power, the risk of manipulating the litigation process evaporates. In addition, the deliberative burdens of the Senate's intervening and independent advice-and-consent role extinguish the strategic concerns animating the voluntary-cessation doctrine in the first place. Cf. Clarke v. United States , 915 F.2d 699, 705 (D.C. Cir. 1990) (en banc) (raising "serious doubts" about "applying the doctrine to Congress" because, "in the absence of overwhelming evidence (and perhaps not then), it would seem inappropriate for the courts either to impute such manipulative conduct to a coordinate branch of government, or to apply against that branch a doctrine that appears to rest on the likelihood of a manipulative purpose"); United States Dep't of the Treasury v. Galioto , 477 U.S. 556, 560, 106 S.Ct. 2683, 91 L.Ed.2d 459 (1986) (analyzing the mooting effects of Congressional amendment without reference to voluntary cessation). At the very least, Codrea has a vanishingly low likelihood of prevailing on that theory. In sum, because Codrea has shown no likelihood of success on his appointment-based challenges due to Attorney General Barr's independent and unchallenged ratification of the Bump-Stock Rule, the district court did not abuse its discretion in denying a preliminary injunction based on those statutory and constitutional claims. B We next consider the plaintiffs' contention that the Bureau lacked statutory authority to promulgate the Bump-Stock Rule. Specifically, Guedes and Codrea argue that the statutory definition of "machinegun" cannot be read to include bumpstock devices. Guedes and Codrea have not demonstrated a substantial likelihood of success on that claim. 1 At the outset, we must determine the standard by which to assess the Rule's conclusion that bump-stock devices amount to "machineguns" under the statutory definition. In particular, should we examine the Rule's conclusion to that effect under the Chevron framework, or is Chevron inapplicable? If Chevron treatment is in order, we first ask if the statute is ambiguous concerning whether bump-stock devices can be considered "machineguns"; and if so, we sustain the Rule's conclusion that bump-stock devices are machine guns as long as it is reasonable. See , e.g. , Entergy Corp. v. Riverkeeper, Inc. , 556 U.S. 208, 218, 129 S.Ct. 1498, 173 L.Ed.2d 369 (2009). Crucially, at this second step under Chevron , an "agency need not adopt * * * the best reading of the statute, but merely one that is permissible." Dada v. Mukasey , 554 U.S. 1, 29 n.1, 128 S.Ct. 2307, 171 L.Ed.2d 178 (2008). Conversely, if Chevron 's two-step framework is inapplicable, we accept the agency's interpretation only if it is the best reading of the statute. Much, then, can turn on whether an agency's interpretation merits treatment under Chevron . For that reason, and because none of the parties presents an argument for applying the Chevron framework (the plaintiffs contend that Chevron is inapplicable and the government does not argue otherwise), we devote considerable attention to the question of Chevron 's applicability to the Bump-Stock Rule. We conclude that the Rule warrants consideration under Chevron . a The applicability of Chevron materially depends on what kind of rule the Bump-Stock Rule represents. There is a "central distinction" under the Administrative Procedure Act between legislative rules and interpretive rules. Chrysler Corp v. Brown , 441 U.S. 281, 301, 99 S.Ct. 1705, 60 L.Ed.2d 208 (1979) ; see 5 U.S.C. § 553(b), (d). And that distinction centrally informs the applicability of Chevron . "Legislative rules generally receive Chevron deference," Nat'l Mining Ass'n v. McCarthy , 758 F.3d 243, 251 (D.C. Cir. 2014), whereas "interpretive rules * * * enjoy no Chevron status as a class," United States v. Mead Corp. , 533 U.S. 218, 232, 121 S.Ct. 2164, 150 L.Ed.2d 292 (2001) ; see also Nat'l Mining Ass'n , 758 F.3d at 251 (observing that interpretive rules "often do not" receive Chevron deference). Legislative rules result from an agency's exercise of "delegated legislative power" from Congress. Am. Mining Cong. v. Mine Safety & Health Admin. , 995 F.2d 1106, 1109 (D.C. Cir. 1993). Accordingly, legislative rules have the "force and effect of law." Encino Motorcars, LLC v. Navarro , --- U.S. ----, 136 S.Ct. 2117, 2122, 195 L.Ed.2d 382 (2016). Interpretive rules, on the other hand, are "issued by an agency to advise the public of the agency's construction of the statutes and rules which it administers." Shalala v. Guernsey Mem'l Hosp. , 514 U.S. 87, 99, 115 S.Ct. 1232, 131 L.Ed.2d 106 (1995). Because they are not an exercise of delegated legislative authority, interpretive rules "do not have the force and effect of law and are not accorded that weight in the adjudicatory process." Id. While legislative rules generally require notice and comment, interpretive rules need not issue pursuant to any formalized procedures. See 5 U.S.C. § 553(b). To determine whether a rule is legislative or interpretive, we ask whether the agency "intended" to speak with the force of law. Encino Motorcars , 136 S.Ct. at 2122 ; Am. Mining Cong. , 995 F.2d at 1109. Central to the analysis is the "language actually used by the agency." Cmty. Nutrition Inst. v. Young , 818 F.2d 943, 946 (D.C. Cir. 1987) (per curiam). We also consider "whether the agency has published the rule in the Code of Federal Regulations" and "whether the agency has explicitly invoked its general legislative authority." Am. Mining Cong. , 995 F.2d at 1112. All pertinent indicia of agency intent confirm that the Bump-Stock Rule is a legislative rule. The Rule unequivocally bespeaks an effort by the Bureau to adjust the legal rights and obligations of bump-stock owners-i.e., to act with the force of law. The Rule makes clear throughout that possession of bump-stock devices will become unlawful only as of the Rule's effective date, not before. To that end, the Rule informs bump-stock owners that their devices "will be prohibited when this rule becomes effective." 83 Fed. Reg. at 66,514 (emphasis added). It correspondingly assures bump-stock owners that "[a]nyone currently in possession of a bump-stock-type device is not acting unlawfully unless they fail to relinquish or destroy their device after the effective date of this regulation." Id. at 66,523 (emphasis added). And the Rule "provides specific information about acceptable methods of disposal, as well as the timeframe under which disposal must be accomplished to avoid violating 18 U.S.C. § 922(o) ." Id. at 66,530 (emphasis added). Reinforcing the point, the Rule says it will "criminalize only future conduct, not past possession of bumpstock-type devices that ceases by the effective date." Id. at 66,525 (emphasis added). Those statements, and others like them in the Rule, embody an effort to "directly govern[ ] the conduct of members of the public, affecting individual rights and obligations." Long Island Care at Home, Ltd. v. Coke , 551 U.S. 158, 172, 127 S.Ct. 2339, 168 L.Ed.2d 54 (2007) (internal quotation marks omitted). That is powerful evidence that the Bureau "intended [the Rule] as a binding application of its rulemaking authority." Id. The Bureau further evinced its intent to exercise legislative authority by expressly invoking the Chevron framework and then elaborating at length as to how Chevron applies to the Rule. The Rule observes that, "[w]hen a court is called upon to review an agency's construction of the statute it administers, the court looks to the framework set forth in Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc. " 83 Fed. Reg. at 66,527. The Rule then contains several paragraphs of analysis describing the application of each of Chevron 's two steps to the Rule. That discussion is compelling evidence that the Bureau did not conceive of its rule as merely interpretive. Because "interpretive rules * * * enjoy no Chevron status as a class," Mead , 533 U.S. at 232, 121 S.Ct. 2164, the Bureau's exegesis on Chevron would have served no purpose unless the agency intended the Rule to be legislative in character. Other evidence of agency intent points to the same conclusion. One consideration under our decisions is "whether the agency has explicitly invoked its general legislative authority." Am. Mining Cong. , 995 F.2d at 1112. The Rule does exactly that, invoking two separate delegations of legislative authority. See 83 Fed. Reg. at 66,515. The first is 18 U.S.C. § 926(a), which empowers the Attorney General to "prescribe only such rules and regulations as are necessary to carry out the provisions of [the Gun Control Act]." The second is 26 U.S.C. § 7805(a), which grants the Attorney General authority to "prescribe all needful rules and regulations" for the enforcement of the National Firearms Act. See 26 U.S.C. § 7801(a)(2)(A). Both of those provisions, the Rule states, vest "the responsibility for administering and enforcing the NFA and GCA" in the Attorney General. 83 Fed. Reg. at 66,515. The Rule's publication in the Code of Federal Regulations also indicates that it is a legislative rule. See Am. Mining Cong. , 995 F.2d at 1112. By statute, publication in the Code of Federal Regulations is limited to rules "having general applicability and legal effect ." 44 U.S.C. § 1510 (emphasis added). The Bump-Stock Rule amends three sections of the Code, modifying the regulatory definition of "machine gun" and "adding a sentence to clarify that a 'machine gun' includes * * * a bump-stock-type device." 83 Fed. Reg. at 66,519 (amending 27 C.F.R. §§ 447.11, 478.11, 479.11 ). Those sorts of amendments would be highly unusual for a mere interpretive rule. In short, the Rule confirms throughout, in numerous ways, that it intends to speak with the force of law. It contained all of those indicia uniformly conveying its intended legislative character when Acting Attorney General Whitaker issued it. And it still contained those indicia when Attorney General Barr subsequently ratified it. Notwithstanding all of that, the government's litigating position in this case seeks to reimagine the Rule as merely interpretive. The government's briefing says that the Rule is "not an act of legislative rulemaking," and that the Rule instead only "sets forth the agency's interpretation of the best reading of the statutory definition of 'machinegun.' " Gov't Br. 38. The government's position to that effect has highly significant implications for owners of bump-stock devices. Whereas a legislative rule, as an exercise of delegated lawmaking authority, can establish a new legal rule going forward, an interpretive rule by nature simply communicates the agency's interpretation of what a statute has always meant. So here, if the Bump-Stock Rule is merely interpretive, it conveys the government's understanding that bump-stock devices have always been machine guns under the statute. The government says exactly that in its brief, observing that, per the interpretation set out in the Rule, "any bump stock made after 1986 has always been a machinegun." Gov't Br. 38. That in turn would mean that bump-stock owners have been committing a felony for the entire time they have possessed the devices. Under 18 U.S.C. § 922(o)(1), it is "unlawful for any person to transfer or possess a machinegun," and violators "shall be fined [or] imprisoned not more than 10 years, or both," id. § 924(a)(2). As the government acknowledges, under the view it espouses in its brief that the Rule is interpretive, the possession of bump stocks "has always been banned." Gov't Br. 38. And that would be so notwithstanding a number of prior contrary interpretations by the agency. See 83 Fed. Reg. at 13,444-13,446. The government's account of the Rule in its brief-including its position that bump-stock owners have always been felons-is incompatible with the Rule's terms. The Rule gives no indication that bump stocks have always been machine guns or that bump-stock owners have been committing a felony for the entire time they have possessed the device. The Rule in fact says the opposite. After all, it establishes an effective date, after which (and only after which) bump-stock possession will be prohibited. 83 Fed. Reg. at 66,523. A future effective date of that kind cannot be reconciled with a supposed intent to convey that bump-stock possession "has always been banned." Gov't Br. 38. The government now characterizes the Rule's effective date as merely marking the end of a period of discretionary withholding of enforcement, in that the Rule informs the public that the Department will "not pursue enforcement action against individuals who sold or possessed bump stocks prior to the effective date." Id. at 38-39. Once again, that is not what the Rule says. The government engages in enforcement discretion when it voluntarily refrains from prosecuting a person even though he is acting unlawfully . The Rule, by contrast, announces that a person "in possession of a bumpstock type device is not acting unlawfully unless they fail to relinquish or destroy their device after the effective date of this regulation." 83 Fed. Reg. at 66,523 (emphases added). That is the language of a legislative rule establishing when bump-stock possession will become unlawful, not an interpretive rule indicating it has always been unlawful. In short, the government cannot now, in litigation, reconceive the Bump-Stock Rule as an interpretive rule. The character of a rule depends on the agency's intent when issuing it, not on counsel's description of the rule during subsequent litigation. See Encino Motorcars , 136 S.Ct. at 2122 ; cf. SEC v. Chenery Corp. , 318 U.S. 80, 87-88, 63 S.Ct. 454, 87 L.Ed. 626 (1943). Here, that intent is unmistakable: the Bump-Stock rule is a legislative rule. b Ordinarily, legislative rules receive Chevron deference. See Nat'l Mining Ass'n , 758 F.3d at 251. This legislative rule is no different. The Supreme Court has established that we afford Chevron deference if we determine (i) "that Congress delegated authority to the agency generally to make rules carrying the force of law," and (ii) "that the agency interpretation claiming deference was promulgated in the exercise of that authority." Mead , 533 U.S. at 226-227, 121 S.Ct. 2164 (2001). Here, both are true. First, we know Congress intended a delegation of legislative authority to the agency because Congress made the relevant delegations express. As noted, the Attorney General has the power to prescribe "such rules and regulations as are necessary to carry out the provisions of" the Gun Control Act. 18 U.S.C. § 926(a). And the Attorney General "shall prescribe all needful rules and regulations for the enforcement of" the National Firearms Act. 26 U.S.C. § 7805(a) ; see id. § 7801(a)(2)(A). "[A] general conferral of rulemaking authority" of that variety "validate[s] rules for all the matters the agency is charged with administering." City of Arlington v. FCC , 569 U.S. 290, 306, 133 S.Ct. 1863, 185 L.Ed.2d 941 (2013). The Supreme Court has said exactly that for § 7805(a), one of the delegations of authority at issue. Specifically discussing that very provision, the Court explained that it has "found such 'express congressional authorizations to engage in the process of rulemaking' to be 'a very good indicator of delegation meriting Chevron treatment.' " Mayo Found. for Med. Educ. & Research v. United States , 562 U.S. 44, 57, 131 S.Ct. 704, 178 L.Ed.2d 588 (2011) (quoting Mead , 533 U.S. at 229, 121 S.Ct. 2164 ). Second, we know that the Bureau promulgated the Bump-Stock Rule "in the exercise of that authority" to "make rules carrying the force of law" because that criterion is the defining characteristic of a legislative rule. Mead , 533 U.S. at 227, 121 S.Ct. 2164. And we have already determined that the Rule is legislative in character. We are then firmly within Chevron 's domain. Nonetheless, the parties protest the applicability of Chevron on several grounds. The plaintiffs first argue that Chevron deference has been waived or forfeited by the government. Next, the parties (including the government) submit that Chevron deference is inapplicable in the context of criminal statutes. And finally, Guedes contends that Chevron deference for criminal statutes is displaced by the rule of lenity. None of those objections to applying Chevron , we conclude, is likely to succeed in the context of the Bump-Stock Rule. (i) The agency plainly believed it was acting in a manner warranting Chevron treatment given that it expressly invoked the Chevron framework in the Rule. The plaintiffs assert that the government nonetheless has forfeited, or even waived, the application of Chevron deference by declining to argue for it in this litigation. And while the government has not taken a definitive position before us on whether Chevron can be waived or forfeited, it has declined to invoke Chevron throughout the course of the litigation. In particular, in its briefing before the district court, the government expressly disclaimed any entitlement to Chevron deference. And after the district court nonetheless relied on Chevron to affirm the Rule, the government filed notices in other pending challenges to the Rule, stating that it "ha[s] not contended that the deference afforded under Chevron * * * applies in this action.'" E.g. , Notice of Supplemental Authority at 2, Gun Owners of Am., Inc. v. Barr , No. 1:18-cv-1429 (W.D. Mich. Feb. 27, 2019), ECF No. 38. Now, in this appeal, the government affirmatively disclaims any reliance on Chevron . See Gov't Br. 37. And at oral argument, the government went so far as to indicate that, while it believes the Rule should be upheld as the best reading of the statute without any need for Chevron deference, if the Rule's validity turns on the applicability of Chevron , it would prefer that the Rule be set aside rather than upheld under Chevron . Oral Argument at 42:38-43:45. To the extent Chevron treatment can be waived, we assume that the government's posture in this litigation would amount to a waiver rather than only a forfeiture. See Wood v. Milyard , 566 U.S. 463, 470 n.4, 132 S.Ct. 1826, 182 L.Ed.2d 733 (2012) ("A waived claim or defense is one that a party has knowingly and intelligently relinquished; a forfeited plea is one that a party has merely failed to preserve."). But our court has yet to address whether, when an agency promulgates a rule that would otherwise plainly occasion the application of Chevron , agency counsel could nonetheless opt to effect a waiver of Chevron treatment when later defending against a challenge to the rule. We have, however, held that an agency's lawyers cannot forfeit the applicability of Chevron deference unless the underlying agency action fails to "manifests its engagement in the kind of interpretive exercise to which review under Chevron generally applies-i.e., interpreting a statute it is charged with administering in a manner (and through a process) evincing an exercise of its lawmaking authority." SoundExchange, Inc. v. Copyright Royalty Bd. , 904 F.3d 41, 54 (D.C. Cir. 2018). We grounded our holding in the principle that "it is the expertise of the agency, not its lawyers," that underpins Chevron . Id. (quoting Peter Pan Bus Lines, Inc. v. Fed. Motor Carrier Safety Admin. , 471 F.3d 1350, 1354 n.3 (D.C. Cir. 2006) ); see also Chenery , 318 U.S. at 87-88, 63 S.Ct. 454. We see no reason that the same limitations on forfeiture of Chevron should not also govern waiver of Chevron . Forfeiture and waiver involve, respectively, a failure to invoke, or an affirmative decision not to invoke, a party's "right or privilege." Johnson v. Zerbst , 304 U.S. 458, 464, 58 S.Ct. 1019, 82 L.Ed. 1461 (1938). But Chevron is not a "right" or "privilege" belonging to a litigant. It is instead a doctrine about statutory meaning-specifically, about how courts should construe a statute. If a statute contains ambiguity, Chevron directs courts to construe the ambiguity as "an implicit delegation from Congress to the agency to fill in the statutory gaps." FDA v. Brown & Williamson Tobacco Corp. , 529 U.S. 120, 159, 120 S.Ct. 1291, 146 L.Ed.2d 121 (2000). If there is ambiguity, the meaning of the statute becomes whatever the agency decides to fill the gaps with, as long as the agency's interpretation is reasonable and "speak[s] with the force of law." Mead , 533 U.S. at 229, 121 S.Ct. 2164. And insofar as Chevron concerns the meaning of a statute, it is an awkward conceptual fit for the doctrines of forfeiture and waiver. We, for example, would give no mind to a litigant's failure to invoke interpretive canons such as expressio unius or constitutional avoidance even if she intentionally left them out of her brief. "[T]he court is not limited to the particular legal theories advanced by the parties, but rather retains the independent power to identify and apply the proper construction of governing law." Kamen v. Kemper Fin. Servs., Inc. , 500 U.S. 90, 99, 111 S.Ct. 1711, 114 L.Ed.2d 152 (1991). The "independent power" to identify and apply the correct law presumably includes application of the Chevron framework when determining the meaning of a statute. Allowing an agency to freely waive Chevron treatment in litigation also would stand considerably in tension with basic precepts of administrative law. As we have explained, a legislative rule qualifying for Chevron deference remains legislative in character even if the agency claims during litigation that the rule is interpretive: Chenery instructs that the proper subject of our review is what the agency actually did, not what the agency's lawyers later say the agency did. See 318 U.S. at 87-88, 63 S.Ct. 454. Accordingly, we have held that a particular rule is legislative rather than interpretive over the protestations of the agency. See, e.g. , Cmty. Nutrition Inst. , 818 F.2d at 946. And once we conclude that a rule is legislative, it follows that we generally review the rule's validity under the Chevron framework. See Nat'l Mining Ass'n , 758 F.3d at 251. A waiver regime, moreover, would allow an agency to vary the binding nature of a legislative rule merely by asserting in litigation that the rule does not carry the force of law, even though the rule speaks to the public with all the indicia of a legislative rule. Agency litigants then could effectively amend or withdraw the legal force of a rule without undergoing a new notice-and-comment rulemaking. That result would enable agencies to circumvent the Administrative Procedure Act's requirement "that agencies use the same procedures when they amend or repeal a rule as they used to issue the rule in the first instance." Perez v. Mortg. Bankers Ass'n , --- U.S. ----, 135 S.Ct. 1199, 1206, 191 L.Ed.2d 186 (2015). And an agency could attempt to secure rescission of a policy it no longer favors without complying with the Administrative Procedure Act, or perhaps could avoid the political accountability that would attend its own policy reversal by effectively inviting the courts to set aside the rule instead. We thus conclude, consistent with SoundExchange 's approach to forfeiture of Chevron , that an agency's lawyers similarly cannot waive Chevron if the underlying agency action "manifests its engagement in the kind of interpretive exercise to which review under Chevron generally applies." SoundExchange , 904 F.3d at 54. In that event, we "apply Chevron * * * even if there is no invocation of Chevron in the briefing in our court." Id. In this case, the Bump-Stock Rule plainly indicates the agency's view that it was engaging in a rulemaking entitled to Chevron deference. That observation naturally follows from the Rule's legislative character, which generally yields treatment under Chevron . See Nat'