KING, Circuit Judge:

The opinion in this case filed on March 23, 2010, Martin v. Halliburton, 601 F.3d 381 (5th Cir.2010), is amended by the addition thereto of a new paragraph II.E, and the opinion, as amended, reads as follows:

Defendants-appellants, affiliated governmental contractors providing logistical support to the United States Army in Iraq, appeal the denial of their Rule 12(b)(1) motion to dismiss for lack of subject matter jurisdiction. Plaintiffs-appellees move to dismiss the appeal for lack of subject matter jurisdiction. We lack subject matter jurisdiction and must dismiss the appeal.

I. BACKGROUND

A. Factual Background

This case reaches us still in its infancy, and the record is accordingly underdeveloped. The facts that follow are drawn primarily from the complaint below and from attachments to motions filed in the district court.

Defendants1 are affiliated governmental contractors providing logistical support to the United States military in Iraq. Plaintiff-appellee Kristen Martin is the adult daughter of Donald Tolfree, a civilian employed by Defendants. Tolfree was recruited by Defendants in December 2006 to drive trucks in convoys in Iraq. Martin alleges that Tolfree relied on Defendants' assurances that he would be 100% safe and protected by the United States military during his employment in Iraq. Tolfree arrived in Iraq in January 2007, where he was assigned to Logistics Support Area (LSA) Anaconda. In February 2007, he was asked if he would volunteer to drive a "chase truck" in an upcoming convoy.2 Tolfree agreed to do so.

Martin's complaint alleges that Defendants acted negligently in executing the convoy operation. According to Martin's complaint, there was no written policy regarding the use of chase trucks, and Tolfree—who had been onsite for less than one month—was not told of any unwritten policies. Tolfree believed that his duty was to follow the convoy from its departure point within LSA Anaconda to the base's north gate, a distance of about ten miles. He believed that he would be contacted by radio and instructed to turn around at the appropriate time. Tolfree's chase truck was equipped with a non-military radio, and a radio dead zone prevents non-military radio communications around the perimeter of LSA Anaconda. As a result, Tolfree followed the convoy past the north gate, at which point Defendants radioed for "the extras" to turn around. Tolfree did so, passing at least two vehicles at the rear of the convoy. The drivers of those vehicles confirmed with the convoy commander that the extra trucks were no longer to be part of the convoy. The convoy commander did not contact the sentry posted at the north gate about Tolfree's return.

Military protocol requires trucks such as the one Tolfree was driving to be accompanied by gun trucks during a return to camp. The sentry posted at the north gate of LSA Anaconda saw Tolfree's chase truck returning and, noting that none of Defendants' trucks was scheduled to enter the camp, applied protocol for dealing with unscheduled and unescorted vehicles attempting to enter LSA Anaconda. Tolfree died instantly when a gunner fired one hundred .50-caliber rounds into the chase truck.

Martin alleges that a representative of Defendants falsely informed her that Tolfree had been killed by an insurgent's roadside bomb rather than by friendly fire. Her complaint alleges that Defendants continued to misrepresent the circumstances of Tolfree's death as late as a year after the fact.

B. The Logistics Civil Augmentation Program

Defendants' involvement in convoy operations in Iraq occurs under the auspices of the Logistics Civil Augmentation Program (LOGCAP). In 1985, the United States Army issued Army Regulation 700-137, which initiated LOGCAP. Army Reg. 700-137, at 1-1 (Dec. 16, 1985). The LOGCAP regulations describe LOGCAP's purpose as "to preplan for the use of civilian contractors to perform selected services in wartime to augment Army forces. Utilization of civilian contractors in a theater of operation will release military units for other missions or fill shortfalls." Id. The LOGCAP regulations expressly state that "[c]ontractors will not be used to perform inherently governmental functions." Id. at 3-2(d)(8). The term "governmental function" is defined as "[a] function which is so intimately related to the public interest as to mandate performance by Government employees. These functions include those activities which require either the exercise of discretion in applying Government authority or the use of value judgments in making decisions for the Government." Id. at Glossary § I.

On December 14, 2001, under the authority of the LOGCAP Program, the Army awarded Contract No. DAAA09-02-D-0007 (the "LOGCAP III Contract") to Brown & Root Services, Inc., a division of Kellogg Brown & Root.3 The LOGCAP III Contract was designated a "rated order" contract, making its performance mandatory under the Defense Production Act of 1950 (DPA), 50 U.S.C. app. §§ 2061-2171. The willful failure to perform a rated order contract carries a criminal penalty. See id. §§ 2071(a) & 2073. Defendants aver that the logistics and transportation services in which Tolfree was engaged were performed pursuant to Task Order 139, issued by the Army in August 2006. Only the first two pages of the LOGCAP III Contract are in the record, and Task Order 139 is completely absent. Martin alleges (and Defendants admit in their answer) that there was a novation of the LOGCAP III Contract in 2003 that transferred contractual duties from Kellogg Brown & Root to Kellogg Brown & Root Services. The two pages from the LOGCAP III Contract that are in the record bear a date stamp of December 14, 2001, which precedes the novation by a minimum of one year.

C. Procedural History

Martin filed a diversity suit in district court on February 5, 2009, asserting state law tort claims against Defendants for their actions in recruiting Tolfree, executing the convoy operation, and misrepresenting the cause of his death.4 On April 3, 2009, Defendants moved to dismiss for lack of subject matter jurisdiction under Rule 12(b)(1) of the Federal Rules of Civil Procedure, urging several distinct theories: (1) official immunity; (2) derivative sovereign immunity; (3) immunity under the DPA; and (4) preemption of state law under the combatant activities exception to the Federal Tort Claims Act (FTCA). Several exhibits were attached to their motion, including two Army regulations, an Army field manual, and two pages of the LOGCAP III Contract.5 The district court denied the motion without opinion or explanation on June 8, 2009.6 Defendants then filed an answer and appealed the district court's order. The record does not reflect that Defendants requested that the district court either explain its decision or certify the decision for interlocutory appeal under 28 U.S.C. § 1292(b).7 Before any briefs had been filed, Martin filed a motion before this court to dismiss the appeal as interlocutory; that motion was carried with the case. The district court ordered further proceedings stayed pending the outcome of this appeal.

II. DISCUSSION

Before we can proceed to the merits of this appeal, we must examine whether we have jurisdiction to do so. We have jurisdiction to determine our own jurisdiction. Henry v. Lake Charles Am. Press, L.L.C., 566 F.3d 164, 169 (5th Cir. 2009) (citing Houston Cmty. Hosp. v. Blue Cross & Blue Shield of Tex., Inc., 481 F.3d 265, 268 (5th Cir.2007)). As the appellants, Defendants bear the burden of establishing our appellate jurisdiction. Acoustic Sys., Inc. v. Wenger Corp., 207 F.3d 287, 289 (5th Cir.2000).

Our appellate jurisdiction is ordinarily limited to "final decisions of the district courts of the United States." 28 U.S.C. § 1291. "For purposes of § 1291, a final judgment is normally deemed not to have occurred until there has been a decision by the District Court that ends the litigation on the merits and leaves nothing for the court to do but execute the judgment." Henry, 566 F.3d at 171 (alterations and internal quotation marks omitted) (quoting Midland Asphalt Corp. v. United States, 489 U.S. 794, 798, 109 S.Ct. 1494, 103 L.Ed.2d 879 (1989)). In addition to our jurisdiction over appeals from final decisions, we have statutory jurisdiction over appeals from certain interlocutory orders and decrees under § 1292(a), but neither party urges the application of that provision. Prospective appellants who seek to appeal interlocutory orders that do not qualify under § 1292(a) are ordinarily limited to the certification procedure of § 1292(b); as noted above, that procedure was not followed here. Thus, our jurisdiction must exist, if at all, under § 1291.

Defendants urge that the collateral order doctrine recognized in Cohen v. Beneficial Industrial Loan Corp., 337 U.S. 541, 69 S.Ct. 1221, 93 L.Ed. 1528 (1949), supports jurisdiction.8 "The collateral order doctrine is best understood not as an exception to the `final decision' rule laid down by Congress in § 1291, but as a `practical construction' of it." Digital Equip. Corp. v. Desktop Direct, Inc., 511 U.S. 863, 867, 114 S.Ct. 1992, 128 L.Ed.2d 842 (1994) (quoting Cohen, 337 U.S. at 546, 69 S.Ct. 1221). "[T]he collateral order doctrine accommodates a `small class' of rulings, not concluding the litigation, but conclusively resolving `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)). "The claims are `too important to be denied review and too independent of the cause itself to require that appellate consideration be deferred until the whole case is adjudicated.'" Id. (quoting Cohen, 337 U.S. at 546, 69 S.Ct. 1221). The Supreme Court, in describing the requirements of the collateral order doctrine, has emphasized the doctrine's limited application:

Will, 546 U.S. at 349-50, 126 S.Ct. 952 (citations and internal quotation marks omitted; alterations in original); see also Mohawk Indus., Inc. v. Carpenter, ___ U.S. ___, 130 S.Ct. 599, 605, 175 L.Ed.2d 458 (2009) ("In applying Cohen's collateral order doctrine, we have stressed that it must `never be allowed to swallow the general rule that a party is entitled to a single appeal, to be deferred until final judgment has been entered.'" (quoting Digital Equip., 511 U.S. at 868, 114 S.Ct. 1992)).

The universe of orders from which collateral order review may be taken is relatively limited.9 The Supreme Court has identified a handful of orders that are collaterally reviewable,10 and we have allowed such review for others.11 Defendants have seized upon the fact that such orders typically involve "denials of various forms of immunity." Henry, 566 F.3d at 177. However, the forms of immunity that may be vindicated on appeal at an early stage through collateral order review are those that involve "not simply a right to prevail, but a right not to be tried." Id. Thus, the relevant inquiry in determining whether an "immunity" is subject to immediate appeal under the collateral order doctrine is whether the asserted immunity is from suit or merely from liability. Van Cauwenberghe v. Biard, 486 U.S. 517, 524, 108 S.Ct. 1945, 100 L.Ed.2d 517 (1988) ("The critical question ... is whether `the essence' of the claimed right is a right not to stand trial." (quoting Mitchell, 472 U.S. at 525, 105 S.Ct. 2806)); Henry, 566 F.3d at 178 ("`There is a crucial distinction between a right not to be tried and a right whose remedy requires the dismissal of charges. A right not to be tried in the sense relevant to the Cohen exception rests upon an explicit statutory or constitutional guarantee that trial will not occur.'" (quoting Midland Asphalt, 489 U.S. at 801, 109 S.Ct. 1494)). Accordingly, the Supreme Court has warned against generalizing from orders that are recognized as immediately appealable under the collateral order doctrine because almost any right can be characterized as a right not to be confronted with the burdens of trial. Will, 546 U.S. at 350-51, 126 S.Ct. 952; Swint v. Chambers County Comm'n, 514 U.S. 35, 43, 115 S.Ct. 1203, 131 L.Ed.2d 60 (1995). Instead, we proceed on a categorical basis, looking only at whether "the class of claims, taken as a whole, can be vindicated by other means" than immediate appeal. Mohawk Indus., 130 S.Ct. at 605.

We must therefore examine each of the rights Defendants asserted before the district court and now seek to appeal to determine whether the district court's denial of that claimed right is a collateral order that Defendants may immediately appeal. In undertaking this jurisdictional analysis, we do not explore the underlying merits of any of the claims Defendants press on appeal.

A. Official Immunity

Defendants first claim that we have jurisdiction to review the denial of their official immunity defense under Westfall v. Erwin, 484 U.S. 292, 108 S.Ct. 580, 98 L.Ed.2d 619 (1988). In Houston Community Hospital, we considered whether such a denial constituted a collateral order. We concluded that "[w]hile a denial of official immunity is an appealable order, the claim of immunity must be `substantial' to justify an appellate court's collateral order review." Houston Cmty. Hosp., 481 F.3d at 268-69 (footnote omitted). To be "substantial," such a claim must be more than "merely `colorable.'" Id. at 269 n. 11.

As originally articulated, the Westfall defense provided that "absolute immunity from state-law tort actions should be available only when the conduct of federal officials is within the scope of their official duties and the conduct is discretionary in nature." Westfall, 484 U.S. at 297-98, 108 S.Ct. 580. Shortly after the Westfall decision, Congress enacted the Federal Employees Liability Reform and Tort Compensation Act of 1988, Pub.L. No. 100-694, 102 Stat. 4563 (1988), one effect of which was to eliminate the requirement that the acts of federal officials be discretionary. See 28 U.S.C. § 2679(d)(1); Houston Cmty. Hosp., 481 F.3d at 269. However, non-governmental entities—such as Defendants—that seek the protection afforded by the Westfall defense remain subject to the requirement that their acts be discretionary. Houston Cmty. Hosp., 481 F.3d at 269. "[B]y `discretionary,' it is evident in context that the [Supreme] Court meant activities that involve `policy-making work for the United States Government.'" NF Indus., Inc. v. Exp.-Imp. Bank of U.S., 846 F.2d 998, 1001 (5th Cir.1988) (per curiam) (quoting Westfall, 484 U.S. at 299, 108 S.Ct. 580). Therefore, to establish our appellate jurisdiction over the denial of their asserted Westfall defense, Defendants must make a substantial showing that their allegedly tortious conduct was within the scope of their official duties and was discretionary in the sense that it involved governmental policy-making activities.

We cannot conclude, based on the limited record before us, that Defendants have made a substantial showing of entitlement to official immunity under Westfall. As discussed above, the LOGCAP regulations expressly provide that "[c]ontractors will not be used to perform inherently governmental functions." Army Reg. 700-137, at 3-2(d)(8). The term "governmental function" is defined as "[a] function which is so intimately related to the public interest as to mandate performance by Government employees. These functions include those activities which require either the exercise of discretion in applying Government authority or the use of value judgments in making decisions for the Government." Id. at Glossary § I (emphases added). This language expressly precludes Defendants from engaging in discretionary conduct, a prerequisite for entitlement to the Westfall defense.12 Defendants cite several actions that they performed—allowing Tolfree's truck to return to LSA Anaconda without coordinating its return and training and supervising employees—but these do not rise to the level of being "activities that involve `policy-making work for the United States Government.'" NF Indus., 846 F.2d at 1001 (quoting Westfall, 484 U.S. at 299, 108 S.Ct. 580). We therefore conclude that we lack jurisdiction over the district court's denial of Westfall immunity.13

B. Derivative Sovereign Immunity

Defendants also claim that the denial of their claim of derivative sovereign immunity "under theories of agency and state action" is an immediately appealable collateral order.14 In Houston Community Hospital, a private insurance carrier under contract with the Government to provide health benefit plans to federal employees sought to appeal the denial of its claim of derivative sovereign immunity. 481 F.3d at 267-68. We held that "a denial of [derivative] sovereign immunity is not subject to immediate review under the collateral order doctrine." Id. at 280. We are bound by this precedent. See United States v. Rose, 587 F.3d 695, 705 (2009) (per curiam). Accordingly, we lack jurisdiction to review the district court's denial of Defendants' claim of derivative sovereign immunity.

C. Defense Production Act

The district court's order also denied Defendants' claim of immunity under § 707 of the DPA, 50 U.S.C. app. § 2157. The DPA authorizes the executive to require the acceptance and priority performance of designated contracts, id. § 2071(a), under threat of criminal penalties, id. § 2073. Section 707 provides:

Id. § 2157. The Supreme Court has noted that § 707 "plainly provides immunity ... [b]y expressly providing a defense to liability...." Hercules, Inc. v. United States, 516 U.S. 417, 429, 116 S.Ct. 981, 134 L.Ed.2d 47 (1996). However, an immunity that merely provides a defense to liability cannot justify collateral order review. See Van Cauwenberghe, 486 U.S. at 524, 108 S.Ct. 1945 ("The critical question ... is whether `the essence' of the claimed right is a right not to stand trial." (quoting Mitchell, 472 U.S. at 525, 105 S.Ct. 2806)); Henry, 566 F.3d at 178.15 Defendants' claim of immunity under § 707 thus fails Cohen's unreviewability prong and "can be adequately vindicated," Mohawk Indus., 130 S.Ct. at 605, on review from a final judgment under § 1291 or using the certification procedure for interlocutory appeal available under § 1292(b).

D. Combatant Activities Exception

Finally, Defendants argue that we have jurisdiction to review the denial of their claim that Martin's causes of action are preempted by the combatant activities exception to the Federal Tort Claims Act (FTCA), 28 U.S.C. § 2680(j). The FTCA abrogates the Government's sovereign immunity for torts committed by its employees in circumstances where, if the Government were a private person, the Government would be liable under state law. 28 U.S.C. §§ 1346(b)(1) & 2674; Villafranca v. United States, 587 F.3d 257, 260 (5th Cir.2009). The Government has not, however, abrogated its sovereign immunity for torts committed by governmental contractors and their employees. 28 U.S.C. § 2671. The combatant activities exception withdraws, in the case of a suit against the Government, both the jurisdictional grant and the abrogation of sovereign immunity for "[a]ny claim arising out of the combatant activities of the military or naval forces, or the Coast Guard, during time of war." Id. § 2680(j).

Defendants argue that the combatant activities exception, which they acknowledge "does not apply directly to government contractors," should be read as preempting Martin's state law claims. They cite the decisions in Saleh v. Titan Corp., 580 F.3d 1 (D.C.Cir.2009), Koohi v. United States, 976 F.2d 1328 (9th Cir. 1992), and Bentzlin v. Hughes Aircraft Co., 833 F.Supp. 1486 (C.D.Cal.1993), as establishing both that state law causes of action against governmental contractors may be preempted by the combatant activities exception and that Martin's state law causes of action should be preempted here. As with Defendants' other defenses, the claim of preemption was denied by the district court, and Defendants seek immediate appeal of that denial under the collateral order doctrine.

While the denial of a claim of preemption by the combatant activities exception may be reviewed on appeal from a final judgment under § 1291 or, in an appropriate case, on interlocutory appeal under § 1292(b), it may not be immediately appealed under the collateral order doctrine. We have previously determined that the denial of a claim that state law is preempted by federal law is not an order that may be immediately appealed under the collateral order doctrine. See Houston Cmty. Hosp., 481 F.3d at 268, 280 (finding no appellate jurisdiction over an uncertified denial of a governmental contractor's summary judgment motion that asserted preemption of a hospital's action by the Federal Employee Health Benefits Act).16 This approach is reflected in the Eleventh Circuit's McMahon decision, which held that the denial of a contractor's claim of preemption under the combatant activities exception is not an immediately appealable collateral order. McMahon, 502 F.3d at 1366 (holding that the court lacked appellate jurisdiction over an uncertified denial of a Rule 12(b)(6) motion to dismiss that asserted preemption by the combatant activities exception).

We conclude, like the Eleventh Circuit in McMahon, that the combatant activities exception is not subject to a sui generis exemption from the ordinary jurisdictional requirements for denials of preemption claims. This conclusion follows from Saleh, on which Defendants rely heavily in pressing their preemption argument. In Saleh, Iraqi nationals who had been imprisoned at the Abu Ghraib military prison during the war in Iraq brought claims against two private military contractors providing interrogation and translation services, respectively, asserting that they had been abused by employees of the contractors. Id. at 1-2. The district court in that case initially denied the contractors' Rule 12 motion to dismiss based on combatant activities preemption because the contractors "ha[d] not produced sufficient factual support to justify [the doctrine's] application." Ibrahim v. Titan Corp., 391 F.Supp.2d 10, 17 (D.D.C.2005) ("Ibrahim I"). The district court ordered limited discovery addressing a number of questions:

Id. at 19. Following a year of discovery, the contractors moved for summary judgment, again asserting preemption. Ibrahim v. Titan Corp., 556 F.Supp.2d 1 (D.D.C.2007) ("Ibrahim II"), aff'd in part, rev'd in part, Saleh, 580 F.3d 1. The district court undertook a fact-intensive analysis and found that the translators had proven that they were entitled to preemption as a matter of law, id. at 10, but that the interrogators had not conclusively demonstrated such an entitlement, id. at 11. On appeal, the Court of Appeals for the District of Columbia Circuit reversed in part, holding that the claims against both contractors were preempted by the combatant activities exception. Saleh, 580 F.3d at 7. However, the court's analysis was—like the district court's—reliant upon the facts obtained through the discovery process. See id. at 4 ("We think the district judge properly focused on the chain of command and the degree of integration that, in fact, existed between the military and both contractors' employees ...."); id. at 10 (considering as significant the military's retention of "command authority [and] operational control over contractors").17

Here, by contrast, we are confronted with circumstances comparable to those present in Ibrahim I—a record too scant to permit an informed decision about the applicability of preemption under the combatant activities exception—that prompted the district court in that case to order limited discovery and development of the factual record. Instructively, the two appeals in Saleh reached the D.C. Circuit using the normal machinery of §§ 1291 and 1292(b)—the plaintiffs whose claims were dismissed on summary judgment against one defendant appealed from a final judgment under § 1291, while the contractor whose summary judgment motion was denied obtained certification for interlocutory appeal under § 1292(b). Id. We agree that an appeal from an appropriately developed and supported interlocutory order denying a claim of preemption under the combatant activities exception may be handled using the certification procedure available under § 1292(b). See id. at 4 (accepting jurisdiction of certified § 1292(b) appeal of order denying claim of combatant activities preemption); see also McMahon, 502 F.3d at 1366; E.I. DuPont de Nemours & Co. v. Sawyer, 517 F.3d 785, 792 (5th Cir.2008) (accepting interlocutory appeal, under § 1292(b), over denial of claims of preemption under the doctrine of San Diego Building Trades Council v. Garmon, 359 U.S. 236, 79 S.Ct. 773, 3 L.Ed.2d 775 (1959), and by provisions of ERISA). That certification procedure was not followed in multiple respects, and we lack jurisdiction to review Defendants' claim that Martin's state law causes of action are preempted.

E. Further Development and Certification

We recognize that many of the immunity and preemption defenses asserted by the Defendants facially satisfy the terms for certification under § 1292(b) in that they "involve[] a controlling question of law as to which there is substantial ground for difference of opinion and ... an immediate appeal ... may materially advance the ultimate termination of the litigation." 28 U.S.C. § 1292(b). Because the basis for many of these defenses is a respect for the interests of the Government in military matters, district courts should take care to develop and resolve such defenses at an early stage while avoiding, to the extent possible, any interference with military prerogatives. Thorough consideration should be given to limiting discovery initially to such defenses. See Saleh, 580 F.3d at 4 (describing the scope of limited discovery under the combatant activities exception). Consideration should also be given to freely certifying orders denying such defenses where the law is unsettled but, after refinement on appeal, might warrant dismissing plaintiffs' claims—provided of course that the record has been developed adequately so that an informed decision can be made about the contours of these defenses. See Hadjipateras v. Pacifica, S.A., 290 F.2d 697, 703 (5th Cir.1961) ("[Section 1292(b) was enacted] to give the appellate machinery ... a considerable flexibility ... so that within reasonable limits disadvantages of piecemeal and final judgment appeals might both be avoided.").

F. Pendent Appellate Jurisdiction

Defendants claim that because they have "established that the District Court's denial of at least one of its asserted defenses is a collateral order, [we] ha[ve] jurisdiction to review all of [Defendant's] asserted defenses" under the pendent appellate jurisdiction doctrine. We disagree that Defendants have established jurisdiction over at least one asserted defense, and we consequently do not assess the propriety of exercising pendent appellate jurisdiction here.

In a similar vein, Martin asserts that only Kellogg Brown & Root is a signatory to the LOGCAP III Contract and that the remaining Defendants are not entitled to immunity or collateral order review of the denial of that immunity. In light of our determination that we lack jurisdiction over any of the claims, we need not address this contention further.

III. CONCLUSION

Defendants have failed to carry their burden of establishing our jurisdiction over any aspect of this interlocutory appeal. Accordingly, we GRANT Martin's motion to dismiss and DISMISS the appeal for lack of subject matter jurisdiction. In doing so, we express no opinion on the merits of Defendants' claims.

The motion to dismiss is GRANTED; the appeal is DISMISSED. Costs shall be borne by Defendants.