Full opinion text
WESLEY, Circuit Judge: In this appeal, Defendants contend that the district court erred in denying their motions for judgment on the pleadings for immunity under New York state law, and their motions for summary judgment for immunity under federal law. We do not have jurisdiction over the state law immunity claims, as the immunity is from liability, not suit. We do have jurisdiction over the federal claims, and hold that the district court did not err in denying Defendants’ motion with respect to these claims. We therefore Dismiss in part, and AffiRM in part. Background A. Procedural History Plaintiffs are construction workers, firefighters, policemen, and others who were present during the clean-up of the World Trade Center after the terrorist attacks of September 11, 2001. In re World Trade Ctr. Disaster Site, 414 F.3d 352, 358 (2d Cir.2005); In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d 520, 557 (S.D.N.Y.2006). Plaintiffs allege that they “were exposed to toxic fumes and gases and other hazardous conditions, and that they suffered respiratory injuries due to the failure of the City and the Port Authority to monitor those conditions and to provide them with adequate safety equipment, and/or to warn them of the hazards.” In re World Trade Ctr. Disaster Site, 414 F.3d at 359. Plaintiffs filed claims against the City of New York (“City”), the Port Authority of New York and New Jersey (“Port Authority”), World Trade Center Properties, and various private companies with whom the City contracted to do much of the work (“Contractor Defendants”), as well as certain additional defendants not at issue in this appeal (collectively, the “Defendants”). Their complaint, as amended, asserts claims for negligence, wrongful death, and for violations of New York Labor and General Municipal Law. In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d at 542. Plaintiffs allege that the City’s Department of Design and Construction (“DDC”) “took control of the site, engaged contractors, and supervised the clean-up operations, but failed to provide adequately for the safety of workers engaged in the clean-up operations.” In re World Trade Ctr. Disaster Site Litig., 469 F.Supp.2d 134, 137 (S.D.N.Y.2007). The cases originated in state court, but Defendants removed the actions to federal court, asserting that the district court had exclusive jurisdiction under the Air Transportation Safety and System Stabilization Act (“ATSSSA”), 49 U.S.C. § 40101 (2006). See In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d at 538. ATSSSA provides a federal cause of action for actions for damages “arising out of’ the terrorist-related aircraft crashes of September 11, 2001, and vests the district courts of the Southern District of New York with “original and exclusive jurisdiction over all actions brought for any claim (including any claim for loss of property, personal injury, or death) resulting from or relating to the terrorist-related aircraft crashes of September 11, 2001.” ATSSSA § 408(b)(3); see also In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d at 538. After the actions were removed to federal court, Plaintiffs filed motions to remand them to state court, which the district court denied. In re World Trade Ctr. Disaster Site Litig., 270 F.Supp.2d 357, 360-61 (S.D.N.Y.2003). The district court determined that “claims for respiratory injury based on exposures suffered at the World Trade Center site between September 11, 2001 and September 29, 2001 ‘arise out of,’ ‘result from,’ and are ‘related to’ the attacks of September 11, 2001,” and, as a result, could only be litigated, pursuant to the ATSSSA, in the Southern District of New York. Id. at 361. The court also held that claims based on exposures either outside the World Trade Center site or after September 29, 2001 were not preempted by the ATSSSA and thus “remain[ed] governed by the New York Labor Law, to be applied in the New York Supreme Court as part of its traditional and historic jurisdiction over New York’s labor laws, or in this court as part of its supplemental jurisdiction ....” Id. The district court, “[c]ognizant ... of the importance of a final determination as to the scope of [its] jurisdiction under the [ATSSSA,] ... certified the order providing for federal jurisdiction for interlocutory appeal, 28 U.S.C. § 1292(b), and stayed the remand of cases not subject to federal jurisdiction pending review by” this Court. In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d at 539 (citing In re World Trade Ctr. Disaster Site Litig., 270 F.Supp.2d at 381). While the appeal of the district court’s ATSSSA preemption order was pending before this Court, the parties entered into discovery, “focusing on Defendants’ anticipated dispositive defense of immunity under state and federal law and with the aim of establishing a joint offer of proof, alleviating Plaintiffs of the burden of proving all factual averments.” Id. Plaintiffs were ordered to file separate claims for each individual claimant after the district court held “that the individual issues relevant to each claimant predominated over common issues.” Id. In deciding the first appeal, this Court noted that, although it did not have jurisdiction over the district court’s remand decision, it disagreed with the district court’s remand order because “the September 29 line of demarcation was not warranted....” In re World Trade Ctr. Disaster Site, 414 F.3d at 371. We invited the district court to reconsider its decision to remand those cases alleging injuries after September 29 and/or in locations other than the World Trade Center site. Id. at 363, 381. The district court then adopted this Court’s reasoning, “without prejudice to future submissions as to the extent of [its] jurisdiction pursuant to the [ATSSSA].” In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d at 539. At a status conference in November of that year, the district court abandoned its effort to require the parties to arrive at a joint offer of proof. Id. The parties were instructed to complete discovery and file their motions regarding Defendants’ affirmative defenses of state and federal statutory and common law immunity. Id. The parties complied. The district court’s resolution of these motions forms the basis of this appeal. The district court determined that the ATSSSA did not preempt “otherwise available” state or federal law immunity defenses. Id. at 545-46. The district court then considered the state and federal immunity claims. In a motion for judgment on the pleadings, Defendants asserted immunity under the New York State Defense Emergency Act (the “SDEA”), the New York State and Local Natural Disaster and Man-Made Disaster Preparedness Law (“Disaster Act”), and New York common law. Id. at 546. Defendants also moved for summary judgment on the federal defenses. Id. at 559. 1. State Immunity Defenses a. SDEA The district court determined that Defendants were not entitled to judgment on their claim for immunity under the SDEA, N.Y. Unconsol. Law § 9102-a. Id. at 547-56. The district court determined that, to be immune under the SDEA, Defendants had to show that they were engaged in civil defense activities, and that those activities were undertaken in good faith “during the rush of emergency.” Id. at 550-52 (quoting Fitzgibbon v. County of Nassau, 147 A.D.2d 40, 541 N.Y.S.2d 845, 849 (1989) and citing N.Y. Unconsol. Law §§ 9193(1); 9103(5)). The district court held that it could not, on the record before it, resolve these fact-sensitive issues. Id. at 554-56. b. Disaster Act The district court held that immunity under the Disaster Act was no broader than under the SDEA and required a similarly fact-intensive inquiry; it denied Defendants’ motion for immunity under the Disaster Act, N.Y. Exec. Law §§ 20-29-g. Id. at 558. c. New York Common Law As with the SDEA and Disaster Act claims, the district court determined that it could not decide as a matter of law whether the City, the Port Authority, and Consolidated Edison were entitled to state common law immunity. Id. at 558-59. 2. Federal Immunity Defenses a. Federal Common Law Immunity Defendants argued that they were entitled to immunity for actions taken in the aftermath of September 11 to the extent that the Army Corps of Engineers (“Army Corps”), the Occupational Safety and Health Administration (“OSHA”), and the Environmental Protection Agency (“EPA”) controlled and directed those actions. Id. at 560. The district court rejected Defendants’ claims that the federal agencies’ assumption of responsibility in developing the protocols for health and safety, without more, extended immunity to Defendants. Id. at 565. However, if Defendants could show that they relied upon the agencies and adopted the federal standards, their conduct would be “tantamount to actions by the federal authority” and they would be entitled to derivative immunity. Id. at 566. Because the court could not, on the record before it, “demark the boundary between federally instructed discretionary decisions, and those made by the various Defendants,” it declined to extend derivative immunity to Defendants. Id. b. Stafford Act The district court also denied Defendants’ motion for summary judgment. It determined that section 305 of the Robert T. Stafford Disaster Relief and Emergency Assistance Act (the “Stafford Act”) did not grant immunity to non-federal actors, or that if the Stafford Act did grant some form of immunity, this immunity was no broader than federal common law immunity. Id. at 566-67. In a later decision construing this order, the district court clarified that it intended to hold “that the Stafford Act did not apply to non-federal actors and therefore did not apply to Defendants in this case,” and that it also denied Defendants derivative Stafford Act immunity. In re World Trade Ctr. Disaster Site Litig., 469 F.Supp.2d at 138, 144. c.Other Bases for Federal Immunity The district court rejected the argument of the Port Authority and World Trade Center Defendants that the federal government’s promise to pay all of the costs associated with the rescue and recovery efforts at the World Trade Center made the government the real party in interest and therefore supported a derivative federal sovereign immunity defense. In re World Trade Ctr. Disaster Site Litig., 456 F.Supp.2d at 567. The court held that while Defendants might ultimately seek indemnification from the federal government, the promise of payment did not suspend the ordinary rules governing the rights and obligations between tortfeasor and victim, and indemnification did not mean Defendants were entitled to immunity. Id. B. Motion to Certify Appeal; Other Proceedings in District Court After the district court decided Defendants’ motions on their immunity defenses, Defendants moved for certification for interlocutory review and then filed a notice of appeal as of right one day later. In re World Trade Ctr. Disaster Site Litig., 469 F.Supp.2d at 137. The district court provisionally denied the motion for interlocutory appeal and rejected Defendants’ claim that the notice of appeal divested it of jurisdiction. Id. In an opinion dated January 8, 2007, the court again held that the notice of appeal was legally ineffective to divest the district court of its jurisdiction, and denied the motion to certify its prior order for interlocutory review. Id. at 145. The court held that Defendants’ appeal did not fall under the collateral order doctrine because it was based on an “unclear and disputed” factual record “and a novel and expanded exception to the rule of finality.” Id. at 140. Noting that 28 U.S.C. § 1292(b) provided for only “limited interlocutory appeals,” the court exercised its discretion to deny Defendants’ motion for an interlocutory appeal, finding that an interlocutory appeal would not “materially advance the ultimate termination of the litigation,” as required by 28 U.S.C. § 1292(b). Id. at 144-45. The delay occasioned by such an appeal would, the district court opined, “be unconscionable, given the intense public interest in reaching an expeditious resolution to this litigation.” Id. at 145. C. The Instant Appeal On November 16, 2006, Defendants appealed to this Court the district court’s denial of the following motions: (1) the City’s motion for judgment on the pleadings based on state statutory and common law immunity; (2) the Port Authority’s motion to dismiss and/or for summary judgment pursuant to the SDEA; (3) the City’s motion for summary judgment based on federal immunity; (4) the Port Authority’s motion for summary judgment dismissing with prejudice Plaintiffs’ actions and all cross-claims against the Port Authority and the World Trade Center Defendants on the ground of federal immunity; and (5) the Port Authority’s motion for judgment on the pleadings based upon state common law immunity. Citing Mitchell v. Forsyth, 472 U.S. 511, 526-27, 105 S.Ct. 2806, 86 L.Ed.2d 411 (1985), which held that immunity from suit is “effectively lost if a case is erroneously permitted to go to trial,” a panel of this Court granted Defendants’ January 17, 2007 motion to divest the district court of jurisdiction by immediately staying all further proceedings before Judge Hellerstein. The panel found it “at least arguable whether some or all of the assertions of immunity put forward by appellants-petitioners have merit.” Plaintiffs then moved to dismiss the appeal for lack of appellate jurisdiction under 28 U.S.C. § 1291, and moved to vacate the stay of the district court proceedings. After oral argument, this Court granted Plaintiffs’ motion to vacate the stay of the district court proceedings, and restored the district court’s jurisdiction for pretrial proceedings and trial while retaining appellate jurisdiction for this panel to decide Defendants’ interlocutory appeal. In re World Trade Ctr. Disaster Site Litig., 503 F.3d 167, 171 (2d Cir.2007). We conclude that the New York defenses are just that: defenses to liability, rather than immunity from suit, and thus not subject to interlocutory appeal. We therefore dismiss that portion of the appeal. We do, however, have jurisdiction to decide the derivative Stafford Act immunity claim. Because we conclude that the district court did not err in denying Defendants’ motion for summary judgment on that issue, we affirm. We also, however, note that the district court erred in determining that Defendants were, as a matter of law, not entitled to derivative Stafford Act immunity. Discussion A. The Final Judgment Rule Plaintiffs argue that the appeal should be dismissed because the district court’s denial of Defendants’ motions is non-final, as the immunities sought do not fall within the “narrow class of decisions” subject to interlocutory review under the collateral order doctrine. Digital Equip. Corp. v. Desktop Direct, Inc., 511 U.S. 863, 867, 114 S.Ct. 1992, 128 L.Ed.2d 842 (1994). They contend that Defendants’ defenses provide only affirmative defenses to liability, are “thoroughly enmeshed with the merits of the case,” and were not finally decided by the district court because that court determined that “factual disputes precluded resolving the defenses at this stage in the case.” As a result, Plaintiffs conclude that we lack jurisdiction over the appeal. 1. The Collateral Order Doctrine Our jurisdiction is generally limited to appeals from “final decisions of the district courts.” 28 U.S.C. § 1291. A final decision “ends the litigation on the merits and leaves nothing for the court to do but execute the judgment.” Van Cauwenberghe v. Biard, 486 U.S. 517, 521, 108 5.Ct. 1945, 100 L.Ed.2d 517 (1988) (quoting Catlin v. United States, 324 U.S. 229, 233, 65 S.Ct. 631, 89 L.Ed. 911 (1945)). “[Ijnterlocutory appeals — appeals before the end of district court proceedings — are the exception, not the rule.” Johnson v. Jones, 515 U.S. 304, 309, 115 S.Ct. 2151, 132 L.Ed.2d 238 (1995). The Supreme Court read into section 1291 Congress’s “express [ion of] a preference that some erroneous trial court rulings go uncorrected until the appeal of a final judgment, rather than having litigation punctuated by ‘piecemeal appellate review of trial court decisions which do not terminate the litigation.’ ” Richardson-Merrell, Inc. v. Roller, 472 U.S. 424, 430, 105 S.Ct. 2757, 86 L.Ed.2d 340 (1985) (quoting United States v. Hollywood Motor Car Co., 458 U.S. 263, 265, 102 S.Ct. 3081, 73 L.Ed.2d 754 (1982)). The Supreme Court has “recognized a ‘small class’ of decisions that are immediately appealable under § 1291 even though the decision has not terminated the proceedings in the district court.” Van Cauwenberghe, 486 U.S. at 522, 108 S.Ct. 1945. This rule, known as the “collateral order” doctrine, was first articulated in Cohen v. Beneficial Industrial Loan Corp., 337 U.S. 541, 546, 69 S.Ct. 1221, 93 L.Ed. 1528 (1949). The collateral order doctrine is a “practical construction” of the final judgment rule, which permits an appellate court to hear an appeal of a decision that would “conclusively resolv[e] ‘claims of right separable from, and collateral to, rights asserted in the action.’ ” Will v. Hallock, 546 U.S. 345, 349, 126 S.Ct. 952, 163 L.Ed.2d 836 (2006) (quoting Behrens v. Pelletier, 516 U.S. 299, 305, 116 S.Ct. 834, 133 L.Ed.2d 773 (1996)). For a court of appeals to have jurisdiction under the collateral order doctrine, the order appealed must (1) “be effectively unreviewable on appeal from a final judgment”; (2) “conclusively determine the disputed question”; and (3) “resolve an important issue completely separate from the merits of the action.” United States v. Aliotta, 199 F.3d 78, 82 (2d Cir.1999) (quoting Midland Asphalt Corp. v. United States, 489 U.S. 794, 799, 109 S.Ct. 1494, 103 L.Ed.2d 879 (1989)). The scope of the collateral order doctrine is “modest.” Will, 546 U.S. at 350, 126 S.Ct. 952. The claims permitted in such an appeal are those that are “too important to be denied review and too independent of the cause itself to require that appellate consideration be deferred until the whole ease is adjudicated.” Cohen, 337 U.S. at 546, 69 S.Ct. 1221; see also Will, 546 U.S. at 349, 126 S.Ct. 952. a. The Requirement of Effective Unreviewability on Appeal from Final Judgment Parties seeking to establish collateral order jurisdiction commonly seek to satisfy the Cohen requirement that a claim be effectively unreviewable on appeal from a final judgment by asserting that they have a “right not to stand trial” or an “immunity from suit,” because both are “effectively lost if a case is erroneously permitted to go to trial.” See Mitchell, 472 U.S. at 525-26, 105 S.Ct. 2806. The Supreme Court has made it clear that “ § 1291 requires courts of appeals to view claims of a ‘right not to be tried’ with skepticism, if not a jaundiced eye,” Digital Equip., 511 U.S. at 873, 114 S.Ct. 1992, for “virtually every right that could be enforced appropriately by pretrial dismissal might loosely be described as conferring a ‘right not to stand trial,’ ” id.; see also Will, 546 U.S. at 351, 126 S.Ct. 952. “[Ojnly explicit statutory and constitutional immunities” from suit may be immediately appealed. Digital Equip., 511 U.S. at 875, 114 S.Ct. 1992. An appellate court must make “a judgment about the value of the interests that would be lost through rigorous application of a final judgment requirement.” Id. at 878-79, 114 S.Ct. 1992; see also Will, 546 U.S. at 351-52, 126 S.Ct. 952. In Will, the Court explained why it had permitted collateral appeal in only a few exceptional categories of cases. Id. at 350-52, 126 S.Ct. 952. Each category recognized “some particular value of a high order” that supported “the interest in avoiding trial: honoring the separation of powers, preserving the efficiency of government and the initiative of its officials, respecting a State’s dignitary interests, and mitigating the government’s advantage over the individual.” Id. at 352, 126 S.Ct. 952. As the Will Court made clear, “it is not mere avoidance of a. trial, but avoidance of a trial that would imperil a substantial public interest, that counts when asking whether an order is ‘effectively’ unreviewable if review is to be left until later.” Id. at 353, 126 S.Ct. 952 (citing Coopers & Lybrand v. Livesay, 437 U.S. 463, 468, 98 S.Ct. 2454, 57 L.Ed.2d 351 (1978)). In Mitchell, for example, a denial of a qualified immunity defense was immediately appealable due to the “threatened disruption of governmental functions, and fear of inhibiting able people from exercising discretion in public service if a full trial were threatened whenever they acted reasonably in the face of law that is not ‘clearly established.’ ” Id. at 352, 126 S.Ct. 952 (citing Mitchell, 472 U.S. at 526, 105 S.Ct. 2806). The government employee’s “distraction ... from ... dut[y]” occasioned by defending a lawsuit is a sufficiently important factor to warrant immediate appeal. Mitchell, 472 U.S. at 526, 105 S.Ct. 2806 (quoting Harlow v. Fitzgerald, 457 U.S. 800, 816, 102 S.Ct. 2727, 73 L.Ed.2d 396 (1982)). However, the costs associated with unnecessary litigation are insufficiently important to warrant the immediate appeal of a pretrial order. Lauro Lines S.R.L. v. Chasser, 490 U.S. 495, 499, 109 S.Ct. 1976, 104 L.Ed.2d 548 (1989). b. The Requirement that the Order Conclusively Determine the Disputed Question and Resolve an Important Issue Completely Separate from the Merits The collateral order doctrine contains two additional criteria: the order “must conclusively determine the disputed question and that question must involve a claim of right separable from, and collateral to, rights asserted in the action.” Mitchell, 472 U.S. at 527, 105 S.Ct. 2806 (internal alterations, citations, and quotation marks omitted). A district court’s determination that, on the facts as alleged by the plaintiff, the defendant is not immune conclusively determines the defendant’s right to “immunity from suit,” regardless of whether the plaintiff ultimately proves its factual allegations, because the defendant loses its asserted right not to stand trial. See id. “[T]he Cohen ‘separability’ component asks whether the question to be resolved on appeal is ‘conceptually distinct from the merits of the plaintiffs claim.’ ” Behrens, 516 U.S. at 309 n. 3, 116 S.Ct. 834 (quoting Mitchell, 472 U.S. at 527, 105 S.Ct. 2806). Generally, “a question of immunity is separate from the merits of the underlying action for purposes of the Cohen test even though a reviewing court must consider the plaintiffs factual allegations in resolving the immunity issue.” Mitchell, 472 U.S. at 528-29, 105 S.Ct. 2806. Both of these requirements are the basis for the rule that a district court’s denial of immunity from suit is an appeal-able collateral order under 28 U.S.C. § 1291 only “to the extent that it turns on an issue of law.” Id. at 530, 105 S.Ct. 2806. “[A] defendant, entitled to invoke a qualified immunity defense, may not appeal a district court’s summary judgment order insofar as that order determines whether or not the pretrial record sets forth a ‘genuine’ issue of fact for trial.” Johnson, 515 U.S. at 319-20, 115 S.Ct. 2151. Nevertheless, if a lower court determines that there is a dispute regarding material issues of fact that precludes summary judgment on a qualified immunity defense, an appellate court “may still exercise interlocutory jurisdiction if the defendant ... contends that he is entitled to qualified immunity even under plaintiffs version of the facts.” Coons v. Casabella, 284 F.3d 437, 440 (2d Cir.2002) (quoting Tierney v. Davidson, 133 F.3d 189, 194 (2d Cir.1998)) (alteration in original); see also Behrens, 516 U.S. at 313, 116 S.Ct. 834. So long as the defendant asserts “an immunity defense on stipulated facts, facts accepted for purposes of the appeal, or the plaintiffs version of the facts that the district judge deemed available for jury resolution,” we have jurisdiction. Salim v. Proulx, 93 F.3d 86, 90 (2d Cir.1996); see also O’Bert ex rel. Estate of O'Bert v. Vargo, 331 F.3d 29, 38 (2d Cir.2003). B. State Law Defenses The plain language of the SDEA and Disaster Act suggests only a defense to liability. Defendants contend that reliance on the language of the statutes “elevates form over substance.” They point out that the New York legislature would have anticipated that the denial of the SDEA and Disaster Act defenses would be immediately appealable as New York law provides an automatic right of interlocutory appeal. N.Y. C.P.L.R. § 5701. As a result, Defendants take the view that regardless of the language employed in the statute, New York’s appellate procedures in effect result in immunity from suit for New York public actors. They also contend as a policy matter that the SDEA and Disaster Act confer an immunity from suit for discretionary functions to allow responders to a disaster to react to catastrophes without “fear of later second-guessing by the courts.” Plaintiffs focus on the statutory language and also contend that the defenses provided by both the SDEA and the Disaster Act are inherently fact-specific and thus generally incapable of resolution before a trial. 1. Factors to Determine Whether the State Immunities are from Liability or from Suit State substantive law governs the scope of immunity for state law claims, and “federal law determines the appealability of the district court’s order.” Napolitano v. Flynn, 949 F.2d 617, 621 (2d Cir.1991) (citing Budinich v. Becton Dickinson & Co., 486 U.S. 196, 199, 108 S.Ct. 1717, 100 L.Ed.2d 178 (1988)). To determine the nature of the rights conferred by a grant of immunity, a court must consider whether, under the law of the sovereign that provides the immunity, those immunities are intended to be from suit, or just from liability. Id. Under federal law, as explained above, only immunities from suit are “effectively unreviewable” on final appeal. Will, 546 U.S. at 353, 126 S.Ct. 952. Essentially, federal law decides the categories of appealable orders; state law determines if a state law claim, or defense, falls within one of the categories. In Napolitano, government officials appealed a district court’s denial of a Vermont state law qualified immunity defense. 949 F.2d at 621. We noted that if the claims had been brought under federal law, Mitchell would provide the analytical blueprint to resolve the jurisdictional inquiry. Id. We reasoned that if “Vermont law, like federal law, holds that qualified immunity is an immunity from suit rather than simply a defense to substantive liability,” then federal law would permit the appeal. Id. As ‘Vermont law unequivocally follows Mitchell’s, reasoning that qualified immunity is an immunity from suit,” we had jurisdiction under the collateral order doctrine. Id. (citing Murray v. White, 155 Vt. 621, 587 A.2d 975, 978 (1991)). Defendants press that New York’s liberal policy of allowing interlocutory appeals requires us to conclude that they are entitled to immediate appeal. In Napolitano, we considered whether Vermont would allow an immediate appeal of the denial of qualified immunity. Id. But Napolitano was an easy case — Vermont law had expressly adopted the reasoning of Mitchell, and Vermont had long had a judge-made collateral order rule that adopted the federal rule laid out in Cohen. Id. Napolitano noted the obvious: where a state employs a final judgment rule akin to that in the federal system, our effort to discern the scope of a state defense may, in some cases, be informed by state courts’ application of the state’s final judgment rule to the defense. If state and federal appellate procedures are congruent, the application of the state procedures to a state defense may shed some light on the federal appellate jurisdiction question. New York appellate procedures, however, reflect policy choices quite different from the limited collateral appeals permitted in federal court. New York freely allows interlocutory appeals to the Appellate Division. N.Y. C.P.L.R. § 5701(a)(1). In New York courts, avoidance of any trial, not only “a trial that would imperil a substantial public interest,” Will, 546 U.S. at 353, 126 S.Ct. 952, warrants immediate appeal, N.Y. C.P.L.R. § 5701(a)(1). Defendants would be permitted to appeal to the Appellate Division the denial of the subject defenses- — -along with the denial of all other motions, some of which would clearly not fall under the federal collateral order doctrine. Because the Appellate Division’s jurisdiction is not premised on a conclusion that a certain defense provides immunity from suit, New York’s liberal policy of appealability to the Appellate Division is of limited use to our analysis. We therefore caution against placing too much emphasis on state appellate procedures, particularly when the state substantive law question can be easily answered from the clear language of a statute or state court decision. The finality of an order under the collateral order rule is a function of the substance of the right denied — -if the right will be irrevocably lost without an immediate appeal, federal courts have jurisdiction to ensure its vindication by permitting appeal under the collateral order doctrine. In our view, to determine whether these New York state defenses provide immunity from suit or only immunity from liability, we need only consider the statutory language, if any, of each defense, and the cases construing the defense. Having done so, we conclude that evidence is compelling that New York has conferred immunity from liability and not from suit with regard to the defenses asserted. Given the clear indication that, as a substantive matter, the New York Court of Appeals views these immunities as only defenses to liability, we conclude that New York appellate procedures are entitled to little, if any, weight. a. Applying the Factors to this Appeal The SDEA provides, in relevant part: 14 N.Y. Unconsol. Law § 9193(1) (emphasis added). The state, any political subdivision, municipal or volunteer agency, ... or any individual, partnership, corporation, association, trustee, receiver or any of the agents thereof, in good faith carrying out, complying with or attempting to comply with any law, any rule, regulation or order duly promulgated or issued pursuant to this act, any federal law, ... relating to civil defense, including but not limited to activities pursuant thereto ... following attack ... shall not be liable for any injury or death to persons or damage to property as the result thereof. The Disaster Act contains a similar grant of immunity: “A political subdivision shall not be liable for any claim based upon the exercise or performance or the failure to exercise or perform a discretionary function or duty on the part of any officer or employee in carrying out the provisions of this section.” N.Y. Exec. Law § 25(5) (emphasis added). The plain language of the SDEA and Disaster Act therefore suggest that the legislature intended to confer only immunity from liability. The Court of Claims Act employs different language. There, the legislature provided that New York “waives its immunity from liability and action and ... assumes liability and consents to have the same determined in accordance with the same rules of law as applied to actions in the supreme court against individuals or corporations ....” N.Y. Court of Claims Act § 8 (emphasis added). Furthermore, in the years before and after the 1978 enactment of the Disaster Act, the legislature explicitly extended immunity “from liability and action” on a number of occasions. If the legislature intended the SDEA and Disaster Act to provide more than a defense to liability, it would have used language providing for immunity “from liability and action.” This conclusion is borne out by various important policy considerations. New York policy is “to reduce rather than increase the obstacles to the recovery of damages for negligently caused injury or death, whether the defendant be a private person ... or a public body.” Abbott v. Page Airways, 23 N.Y.2d 502, 507, 297 N.Y.S.2d 713, 245 N.E.2d 388 (1969) (citations omitted). Moreover, “[ljegislative grants of privilege are to be liberally interpreted in favor of the public, and strictly interpreted against the grantee; and statutes in derogation of sovereignty are strictly construed.” N.Y. Statutes § 291. Thus, where the New York legislature has quite deliberately provided only for immunity from liability, expanding that immunity also to suits would contravene New York policy. We may not “import immunity back into a statute designed to limit it.” Indian Towing Co. v. United States, 350 U.S. 61, 69, 76 S.Ct. 122, 100 L.Ed. 48 (1955). Thus, the willingness of the legislature to explicitly confer immunity from liability and action in other statutes counsels against reading the SDEA and Disaster Act more broadly here. Likewise, the New York legislature’s extension of immunity from liability and action to certain entities in certain circumstances, see supra n. 15, suggests that New York common law discretionary function immunity does not provide immunity from suit. Construing the current version of the Court of Claims Act’s immunity waiver, the Court of Appeals has noted that [t]he immunity waived by section 8 of the Act is the historic immunity derived from the State’s status as a sovereign and protects the State from suit. The defenses the dissent refers to are based on the special status of the defendant as a governmental entity. The State is amenable to suit but may nevertheless assert these grounds to avoid paying damages for some tortious conduct because, as a matter of policy, the courts have foreclosed liability.... [I]n each of [the cases cited by the dissent,] the Court entertained jurisdiction and decided the matter on the basis of the defense asserted. Brown, 89 N.Y.2d at 192-93, 652 N.Y.S.2d 223, 674 N.E.2d 1129 (citations omitted). The New York Court of Appeals has decided only one case involving the SDEA’s immunity provision, see Abbott, 23 N.Y.2d at 507, 297 N.Y.S.2d 713, 245 N.E.2d 388, and has not construed the Disaster Act’s immunity provision. In Abbott, the director of the county civil defense office chartered a helicopter to observe the “street rioting [that] erupted in Rochester in ... 1964.” Id. at 506, 297 N.Y.S.2d 713, 245 N.E.2d 388. The helicopter crashed, killing the pilot, the director, and two people on the ground. Id. The defendant owner of the helicopter asserted immunity from suit under the SDEA. Id. at 506-07, 297 N.Y.S.2d 713, 245 N.E.2d 388. Affirming the jury’s verdict for the plaintiffs, the Court of Appeals observed that “the policy of this State has been to reduce rather than increase the obstacles to the recovery of damages for negligently caused injury or death, whether the defendant be a private person .’.. or a public body.” Id. at 507, 297 N.Y.S.2d 713, 245 N.E.2d 388 (citations omitted). The court also noted that, under New York law, “[l]iability is the rule, immunity the exception.... The rule of non-liability is out of tune with life about us, at variance with modern-day needs and with concepts of justice and fair dealing.” Id. at 507 n. 2, 297 N.Y.S.2d 713, 245 N.E.2d 388 (quoting Bing v. Thunig, 2 N.Y.2d 656, 666-67, 163 N.Y.S.2d 3, 143 N.E.2d 3 (1957)) (alterations in original). The Court of Appeals’ Abbott decision thus suggests that the state defenses Defendants invoke do not provide immunity from suit. And if they are only defenses to liability, it is clear this Court must dismiss the appeal, as a ruling on these defenses is not cognizable under the collateral order doctrine. We find support for this position in Brown’s broad construction of the state’s waiver of immunity from liability and action. Brown, 89 N.Y.2d at 192, 652 N.Y.S.2d 223, 674 N.E.2d 1129; see N.Y. Court of Claims Act § 8. There, the Court of Appeals held that “legal defenses which the State may interpose to avoid liability,” including the “discretionary actions” defense, while “sometimes referred to loosely as ‘immunities’, should not be confused with sovereign immunity.” Brown, 89 N.Y.2d at 192, 652 N.Y.S.2d 223, 674 N.E.2d 1129. The cases Defendants enlist predate Brown’s clear statement that “[t]he State is amenable to suit but may nevertheless assert these grounds to avoid paying damages for some tortious conduct because, as a matter of policy, the courts have foreclosed liability.” Id. The plain language of the SDEA and the Disaster Act, as well as New York Court of Appeals case law drawn from analogous contexts, support our view that the New York legislature has made a deliberate decision to limit the immunity available under the SDEA and the Disaster Act to immunity from liability. Brown and New York’s policy regarding immunities under state law make clear that common law discretionary function immunity is, likewise, only immunity from liability. 2. The Port Authority’s State Sovereign Immunity Argument Finally, the Port Authority contends that it is entitled to “sovereign immunity” because it was engaged in uniquely governmental activities that were “completely sovereign in nature and completely foreign to any activity which could be carried on by a private person.” Williams v. State, 90 A.D.2d 861, 456 N.Y.S.2d 491, 493 (1982). The Port Authority is a “government-operated body which is responsible for developing public transportation within the statutorily determined Port District.” Japan Airlines Co. v. Port Auth. of N.Y. & N.J., 178 F.3d 103, 107 (2d Cir.1999). It is also the owner of the 16-acre World Trade Center site. The States of New York and New Jersey enacted a broad waiver of sovereign immunity for the Port Authority. See N.Y. Unconsol. Law § 7101 (“[T]he states of New York and New Jersey consent to suits, actions or proceedings of any form or nature at law, in equity or otherwise ... against the Port of New York Authority.”); see also N.J. Stat. Ann. §§ 32:1-162; Port Auth. Trans-Hudson Corp. v. Feeney, 495 U.S. 299, 306, 110 S.Ct. 1868, 109 L.Ed.2d 264 (1990) (citing section 7101 for the conclusion that “New York and New Jersey have expressly consented to suit in expansive terms”). They also enacted a more specific consent to suit for tortious acts by the Port Authority or its agents. See N.Y. Unconsol. Law § 7106 (“Although the port authority is engaged in the performance of governmental functions, the said two states consent to liability on the part of the port authority in such suits, actions or proceedings for tortious acts committed by it and its agents to the same extent as though it were a private corporation.”). Because “New York and New Jersey have expressly consented to suit in expansive terms,” Feeney, 495 U.S. at 306, 110 S.Ct. 1868, the Port Authority “is not entitled to Eleventh Amendment immunity from suit,” Hess v. Port Auth. Trans-Hudson Corp., 513 U.S. 30, 39, 115 S.Ct. 394, 130 L.Ed.2d 245 (1994). Whether the Port Authority might still be entitled to discretionary governmental function immunity in certain circumstances, despite these broad enactments subjecting it to suit, appears to be unresolved. Some courts have simply held that the Port Authority is not immune for governmental functions — whether discretionary or not — because section 7106 contains no limiting language to suggest that it preserved any residual sovereign immunity. See, e.g., Rittenhouse v. A. Star Container Serv., No. 86 CTV 5876, 1988 WL 112898, at *2 (S.D.N.Y. Oct.17, 1988) (“[Section 7106] makes it clear that the Port Authority does not enjoy immunity for tortious acts committed while performing governmental functions.”); In re World Trade Ctr. Bombing Litig., 3 Misc.3d 440, 776 N.Y.S.2d 713, 728 (N.Y.Sup.Ct.2004) (“These claims fall within the broad coverage of the statute, are not specifically excluded, and therefore are authorized under the terms of those sections.”). In another case, without ruling out that the Port Authority could be entitied to governmental immunity, this Court declined to extend such immunity by finding that the alleged claims involved a “proprietary function,” in contrast to a discretionary governmental function, and that there was a “special relationship” between the plaintiffs and Port Authority. See Japan Airlines, 178 F.3d at 111. Regardless of whether the Port Authority could convince a jury, or this Court on appeal after a final judgment, that its actions fall on the government side of the “governmental versus proprietary [function] continuum,” Sebastian v. State, 93 N.Y.2d 790, 796, 698 N.Y.S.2d 601, 720 N.E.2d 878 (1999), Broum makes it clear that any residual discretionary function governmental immunity is merely a defense to liability, rather than an immunity from suit. See Brown, 89 N.Y.2d at 192, 652 N.Y.S.2d 223, 674 N.E.2d 1129 (citing, e.g., Miller v. State, 62 N.Y.2d 506, 510, 478 N.Y.S.2d 829, 467 N.E.2d 493 (1984) (“[A] governmental entity’s conduct may fall along a continuum of responsibility to individuals and society deriving from its governmental and proprietary functions.” Id. at 511-12, 478 N.Y.S.2d 829, 467 N.E.2d 493.)). For these reasons, we conclude that the Port Authority’s asserted state law immunity is not immunity from suit, and it therefore does not permit collateral order appeal. While we do not doubt that Defendants may well “face the prospect of thousands of lawsuits and years of litigation,” we return to the New York Court of Appeals’ decision in Brown: “When the law immunizes official violations of substantive rules because the cost or bother of doing otherwise is too great, thereby leaving victims without any realistic remedy, the integrity of the rules and their underlying public values are called into serious question.” 89 N.Y.2d at 196, 652 N.Y.S.2d 223, 674 N.E.2d 1129. New York disfavors immunities from suit; we must abide by its policy choices. Those choices are clear with respect to the SDEA, Disaster Act, and New York common law: they provide only a defense to liability. As these defenses are not “effectively unreviewable on appeal from a final judgment,” Midland Asphalt, 489 U.S. at 799, 109 S.Ct. 1494, Defendants cannot appeal the denial of those immunities prior to final judgment. That portion of their appeal is therefore dismissed. C. Federal Law Defenses Defendants — with the exception of the Port Authority, discussed infra — appeal only the denial of their motion for summary judgment on Stafford Act discretionary immunity. 1. Whether Stafford Act Immunity is a Collateral Order Subject to Interlocutory Appeal For the district court’s denial of Stafford Act immunity to be “effectively unreviewable on appeal from final judgment,” section 305 of the Stafford Act must confer immunity from suit or its functional equivalent. Once again we start with the language of the statute. See, e.g., United States v. Am. Trucking Ass’ns, 310 U.S. 534, 543, 60 S.Ct. 1059, 84 L.Ed. 1345 (1940). Section 305 of the Stafford Act, titled “Nonliability of Federal Government,” provides: The Federal Government shall not be liable for any claim based upon the exercise or performance of or the failure to exercise or perform a discretionary function or duty on the part of a Federal agency or an employee of the Federal Government in carrying out the provisions of this chapter. 42 U.S.C. § 5148. Elsewhere in Title 42 of the Code, a different section provides that “a covered person shall be immune from suit and liability.” See, e.g., 42 U.S.C. § 247d-6d(a)(l) (amended 2005). At first blush, then — because it makes no reference to immunity from suit — it appears that the Stafford Act confers only a defense to liability. While we are the first circuit to consider the appealability under Cohen of a denial of a Stafford Act defense, two other circuits and several district courts have suggested that the Stafford Act provides immunity from suit. In Rosas v. Brock, the Eleventh Circuit relied upon the legislative history of the Stafford Act to conclude that Congress intended “to preclude judicial review of all disaster relief claims based upon the discretionary actions of federal employees,” in part because it “was concerned ... about ... the certain costs of defending suits arising from government relief.” 826 F.2d 1004, 1008 (11th Cir. 1987). The court relied on the report of Representative Whittington, Chairman of the House Public Works Committee, which stated: We have further provided that if the agencies of the Government make a mistake in the administration of the Disaster Relief Act that the Government may not be sued. Strange as it may seem, there are many suits pending in the Court of Claims today against the Government because of alleged mistakes made in the administration of other relief acts.... We have put a stipulation in here that there shall be no liability on the part of the Government. Id. at n. 1 (quoting H.R. 8396, 81st Cong., 2d Sess., 96 Cong. Rec. 11895, 11912 (1950)) (emphasis added). The Ninth Circuit likewise suggested that section 305 of the Stafford Act conferred immunity from suit. It held that “decisions involving the allocation and deployment of limited governmental resources are the type of administrative judgment that the discretionary function exception was designed to immunize from suit.” Graham v. FEMA, 149 F.3d 997, 1006 (9th Cir.1998) (quoting Fang v. United States, 140 F.3d 1238, 1241-42 (9th Cir.1998)). A district court in this circuit has also opined that “[t]he language of the statute and the legislative history of the Stafford Act clearly preclude discretionary actions taken under the Stafford Act from judicial review.” Benzman v. Whitman, No. 04 cv. 1888, 2006 WL 250527, at *22 (S.D.N.Y. Feb.2, 2006). The Stafford Act is not the only federal statute that provides a “discretionary function” immunity. The Federal Tort Claims Act (“FTCA”) also contains a discretionary function exception. 28 U.S.C. § 2680(a). The statutes employ practically identical language: both provide protection for “the exercise or performance of or the failure to exercise or perform a discretionary function or duty on the part of a [F]ederal agency or an employee of the [Federal] Government....” 42 U.S.C §5148; 28 U.S.C. § 2680(a) (alterations in FTCA). Furthermore, we have previously considered the FTCA in analyzing other discretionary function immunities. See, e.g., In re Joint E. & S. Dists. Asbestos Litig., 891 F.2d 31, 34 (2d Cir.1989) (examining the FTCA to determine that the discretionary function exception should be read into the Suits in Admiralty Act, even though that Act “contain[ed] no express exception for discretionary functions”). Finally, it appears that the discretionary function defense in the Stafford Act was based upon the discretionary function exception in the FTCA. Thus, we consider the policies for the FTCA discretionary function exception, and prior interpretations of that exception, for guidance on the nature of the Stafford Act discretionary function immunity. With its passage of the FTCA in 1946, Congress “waived sovereign immunity from suit for certain specified torts of federal employees.” Dalehite v. United States, 346 U.S. 15, 17, 73 S.Ct. 956, 97 L.Ed. 1427 (1953), partially overruled on other grounds by Rayonier Inc. v. United States, 352 U.S. 315, 77 S.Ct. 374, 1 L.Ed.2d 354 (1957); see also 28 U.S.C. § 2674. “This waiver, however, operates subject to numerous conditions, each of which must be satisfied for a court to exercise jurisdiction.” Adeleke v. United States, 355 F.3d 144, 153 (2d Cir.2004). Exempted from the FTCA’s waiver of sovereign immunity are the classes of claims contained in section 2680, including the discretionary function exception in section 2680(a). United States v. S.A. Empresa de Viacao Aerea Rio Grandense (Vavig Airlines), 467 U.S. 797, 808, 104 S.Ct. 2755, 81 L.Ed.2d 660 (1984). The discretionary function exception “marks the boundary between Congress’ willingness to impose tort liability upon the United States and its desire to protect certain governmental activities from exposure to suit by private individuals.” Id. The Supreme Court has noted that the discretionary function exception was intended to “avoid[] any possibility that the [FTCA] may be construed to authorize damage suits against the Government growing out of a legally authorized activity, merely because the same conduct by a private individual would be tortious.” Dalehite, 346 U.S. at 27, 73 S.Ct. 956 (internal citations omitted). The Supreme Court recognized that this “exception was drafted merely as a ‘clarifying amendment’ to the FTCA, since Congress ‘believed that claims of the kind embraced by the discretionary function exception would have been exempted from the waiver of sovereign immunity by judicial construction.’ ” In re Joint E. & S. Dist. Asbestos Litig., 891 F.2d at 35 (citations omitted). Section 2680(a) protects the “policy judgment[s]” of government officers' — i.e., “the discretion of the executive or the administrator to act according to [his or her] judgment of the best course.” Dalehite, 346 U.S. at 34-36, 73 S.Ct. 956. The discretionary function exception was designed to prevent plaintiffs from testing “the constitutionality of legislation, the legality of regulations, or the propriety of a discretionary administrative act through the medium of a damage suit for tort. The same holds true of other administrative actionfs] not of a regulatory nature, such as ... the execution of a Federal project....” Varig Airlines, 467 U.S. at 809-10, 104 S.Ct. 2755. The FTCA discretionary function exception is thus a form of retained sovereign immunity. As a result, the waiver of federal sovereign immunity does not encompass actions based upon the performance of, or failure to perform, discretionary functions. The Supreme Court’s latest foray in to this area confirms our view. Ali v. Fed. Bureau of Prisons, — U.S.-, 128 S.Ct. 831, 834, 169 L.Ed.2d 680 (2008) (“This case concerns the scope of 28 U.S.C. § 2680, which carves out certain exceptions to the United States’ waiver of sovereign immunity for torts committed by federal employees.”). However, several circuits have suggested that the “sovereign immunity of the United States is not ‘a right not to be sued.’ ” Houston Cmty. Hosp. v. Blue Cross & Blue Shield of Tex., Inc., 481 F.3d 265, 277 (5th Cir.2007). In Houston Community Hospital, the hospital provided care to three federal employees only after obtaining their levels of coverage from Blue Cross, a contract health insurer of the three under the Federal Employees Health Benefits Act (“FEHBA”). When the bills were submitted to Blue Cross by the hospital, Blue Cross refused to pay a substantial portion of each bill. The hospital sued Blue Cross in state court on a state tort theory of negligent misrepresentation and Blue Cross removed to federal court. Blue Cross moved to dismiss on two immunity grounds (official immunity and sovereign immunity of the United States). Id. at 267-68. The district court denied the motion and, without leave from the lower court, Blue Cross filed an appeal with the Fifth Circuit. With regard to the claim of sovereign immunity, the circuit ruled that federal sovereign immunity did not encompass the right not to be sued. Id. at 277. The court relied upon the Seventh Circuit’s decision in Pullman Construction Industries, Inc. v. United States, 23 F.3d 1166 (7th Cir.1994). Id. at 277-78. In Pullman, a bankruptcy debtor sued the United States to recover, as preferential transfers, approximately $500,000 in federal taxes paid to the United States during the 90-day period before bankruptcy. 23 F.3d at 1167. The Seventh Circuit held that the government was not entitled to an interlocutory appeal of the denial of a motion to dismiss on sovereign immunity grounds. Id. at 1169-70. Notwithstanding the federal government’s waiver of immunity under 11 U.S.C. § 106(a), the circuit court undertook a sweeping and entertaining analysis of the concept of sovereign immunity. The government asserted that its claim of immunity from suit was clear' — giving the court jurisdiction to hear the interlocutory appeal. The court, however, was surprised that the appeal in Pullman was the first of its kind. Id. at 1168. Writing for the court, Judge Easter-brook observed that “[djescriptions of the United States’ sovereign immunity often refer to freedom from suit as well as freedom from an obligation to pay damages,” and explained that the genesis of the “right not to be sued” arose from the “newfangled nature of the doctrine permitting appeals based on claims of rights to be free from litigation.” Id. But because the United States Code was “riddled with statutes authorizing relief against the United States and its agencies,” he concluded that “[fjederal sovereign immunity today is nothing but a condensed way to refer to the fact that monetary relief is permissible only to the extent Congress has authorized it.” Id. (citing the FTCA, among other statutes). Any residual sovereign immunity was only a defense to liability that did not entitle the government to immediate appeal under the collateral order doctrine. Id. at 1168-69 (acknowledging the “venerable tradition of litigation between the United States and taxpayers to determine amounts due and recover overpayments”). One should be careful in drawing too broad a conclusion from the Pullman court’s analysis. In our view, Pullman attempts to chart the general state of the law of sovereign immunity in an age of an omnipresent federal government. We read Pullman only to conclude that the traditional concept of sovereign immunity has been whittled away by Congress. It has been replaced by “[a]n elaborate system permitting some monetary claims and limiting or forbidding others.” Id. at 1168 (emphasis added); see also Alaska v. United States, 64 F.3d 1352, 1355 (9th Cir. 1995). The court did not declare that a right not to be sued could not be extended to a category of claims; it simply said that the source of the right had to come from Congress (or the Constitution) and not from a claim of sovereign immunity. We are not convinced that Pullman or its progeny counsel us to disregard the statements of the Supreme Court that sovereign immunity encompasses a right not to be sued, see FDIC v. Meyer, 510 U.S. 471, 475, 114 S.Ct. 996, 127 L.Ed.2d 308 (1994) (“Absent a waiver, sovereign immunity shields the Federal Government and its agencies from suit.”); Minnesota v. United States, 305 U.S. 382, 387, 59 S.Ct. 292, 83 L.Ed. 235 (1939) (“The exemption of the United States from being sued without its consent extends to a suit by a State.”), even though those statements were not made in cases involving interlocutory appeals. But even if one could safely say that the United States has abandoned the traditional concept of sovereign immunity — replacing it with hundreds of statutes that authorize or circumscribe the right to sue the United States, while using the terms “liability” or “action” without any diseernable consistency- — -that view would not end our inquiry. The Stafford Act provides a specific congressional recognition of discretionary function immunity. It is therefore distinguishable from the question of reserved sovereign immunity at issue in Pullman and its progeny. Finally, we must still determine if the Stafford Act discretionary act immunity protects a substantial public interest that would be imperiled if an immediate appeal is not available. In addition, the discretionary function exception serves to protect “the principles embodied in the separation of powers doctrine by keeping the judiciary from deciding questions consigned to the executive and legislative branches of the government.” Caban v. United, States, 671 F.2d 1230, 1233 (2d Cir.1982); see also Andrulonis v. United States, 924 F.2d 1210, 1218 (2d Cir.1991), vacated on other grounds by New York State Dep’t of Health v. Andrulonis, 502 U.S. 801, 112 S.Ct. 39, 116 L.Ed.2d 18 (1991). Separation of powers is “a doctrine to which the courts must adhere even in the absence of an explicit statutory command,” Canadian Transp. Co. v. United States, 663 F.2d 1081, 1086 (D.C.Cir.1980), and “requires that a branch not impair another in the performance of its constitutional duties,” Loving v. United States, 517 U.S. 748, 757, 116 S.Ct. 1737, 135 L.Ed.2d 36 (1996). The discretionary function immunity in the Stafford Act, like its counterpart in the FTCA, is obviously animated by separation of powers concerns. Section 305 of the Stafford Act protects a right — the right of federal agencies to make discretionary decisions when engaged in disaster relief efforts without fear of judicial second-guessing — that is a “particular value of a high order.” Will, 546 U.S. at 352, 126 S.Ct. 952. Denying immediate review of the denial of such an immunity could well result in “a trial that would imperil a substantial public interest.” Id. at 353, 126 S.Ct. 952. The Act provides that the United States will not be liable for those discretionary decisions made under its authority. The nature of those decisions — made during a declared national emergency — raise significant separation of powers concerns if, as a matter of law, the decision was authorized by the Act. To deny an interlocutory appeal in that circumstance would be contrary to the policy concerns first set forth in Cohen and most recently articulated in Will. Although here the Defendants claiming immunity from suit are not federal agencies or officials, our conclusion that section 305 of the Stafford Act provides immunity from suit provides us with collateral order jurisdiction to determine the substantive question of whether that immunity may extend derivatively to non-federal entities working in cooperation with federal agencies under the Stafford Act. Cf. Del Campo v. Kennedy, 517 F.3d 1070, 1074 (9th Cir.2008) (“Whether [Eleventh Amendment] immunity reaches beyond ‘states and state entities’ is the substantive issue we face, which we may not prejudge by denying jurisdiction to decide it.”); McMahon v. Presidential Airways, Inc., 502 F.3d 1331, 1339 (11th Cir.2007) (exercising jurisdiction over a collateral.order appeal by a defendant claiming derivative Feres immunity because the defendant “ha[d] a substantial claim to a true immunity from suit”). Defendants’ claims also satisfy the other two prongs of the Cohen collateral order rule: they “conclusively determine the disputed question” and “resolve an important issue completely separate from the merits of the action.” Will, 546 U.S. at 349, 126 S.Ct. 952. The District Court found that the Army Corps, OSHA, and the EPA each occupied and performed certain leadership roles at the clean-up sites. Defendants contend that they are entitled to derivative Stafford Act immunity based on these facts, which “the District Court deemed sufficiently supported for purposes of summary judgment.” Salim, 93 F.3d at 89 (quoting Behrens, 516 U.S. at 313, 116 S.Ct. 834). The immunity defense is, furthermore, “an important issue completely separate from the merits of the action.” Aliotta, 199 F.3d at 82. Thus, we have jurisdiction over the Stafford Act appeal. 2. Derivative Stafford Act Discretionary Function Immunity Defendants are apparently “the first to claim derivative immunity under the Stafford Act since it was enacted in 1974.” In re World Trade Ctr. Disaster Site Litig., 469 F.Supp.2d at 144. Defendants contend that the Stafford Act immunity should be derivatively extended to non-federal responders to allow these entities to “seamlessly implement the discretionary decisions and instructions of federal experts and agencies.” The. district court’s resolution of Defendants’ asserted federal immunity is somewhat ambiguous. To the extent it held that Defendants. are not entitled to immunity