In this action brought pursuant to § 702 of the Administrative Procedure Act, plaintiffs seek .additional funding for fiscal years (“FYs”) 2007 and 2008 from a grant program administered by the Department of Health and Human Services (“HHS”) pursuant to the Ryan White HIV/AIDS Treatment Modernization Act of 2006. In a previous appeal relating to plaintiffs’ application for a preliminary injunction, we held that they had demonstrated a likelihood of success on the merits. On remand, defendants moved to dismiss plaintiffs’ claims, arguing that HHS had awarded the funds at issue to other grant recipients. The district court verified that the pertinent congressional appropriations *138had, in fact, been exhausted, and held that plaintiffs’ claims are moot.
Despite the seemingly harsh result, we agree with the district court. Obliged, as we are, to avoid issuing advisory opinions, our authority is limited to “live” cases in which there remains a possibility that the court can grant some form of effectual relief. In an action such as this one, the scope of available relief is bookended by the government’s sovereign immunity, on the one hand, and the Appropriations Clause of the Constitution, on the other. Where, as here, the congressional appropriations relating to the funds sought by private litigants have been lawfully distributed- — and therefore exhausted — by a federal agency, courts lack authority to grant effectual relief in the context of an Article III ease or controversy. Under such circumstances, any decision on the ultimate merits of the dispute would be merely advisory, and the claims at issue are moot. Accordingly, we affirm.
I. BACKGROUND
Congress passed the Ryan White Comprehensive AIDS Resources Emergency Act of 1990 (the “Ryan White Act,” or the “Act”), Pub.L. No. 101-381, 104 Stat. 576, in order to make funding available for the development and administration of “cost efficient systems for the delivery of essential services to individuals and families with HIV disease.” 42 U.S.C. § SOOff.1 Part A of the Act, titled “Emergency Relief for Areas with Substantial Need for Services,” directed HHS to award grants to localities that qualified as “Eligible Metropolitan Areas,” or “EMAs.” Pub.L. No. 101-381, pt. A, § 2601, 104 Stat. at 576; see also 42 U.S.C. § SOOff — 11 (1991) (original definition of “EMA”). HHS awarded grants to New York’s Nassau and Suffolk Counties (“Nassau-Suffolk”) as a single EMA in each year through FY 2006.
Fiscal year 2007 began on October 1, 2006. Almost three months later, on December 19, 2006, Congress amended the Ryan White Act by creating a second category of funding-eligible entities, referred to as “Transitional Grant Areas” or “TGAs,” which were to receive less funding than EMAs. Ryan White HIV/AIDS Treatment Modernization Act of 2006, Pub.L. No. 109-415, § 107, 120 Stat. 2767, 2781; see also 42 U.S.C. § 300ff-19. The amendments took effect in FY 2007 and contained a sunset provision that repealed the Act effective October 1, 2009. See County of Nassau, N.Y. v. Leavitt, 524 F.3d 408, 416 (2d Cir.2008).2
HHS typically begins to notify recipients of grants under Part A of the Ryan White Act on March 1 of each fiscal year. With respect to FY 2007, however, the agency informed Nassau-Suffolk on February 12, 2007 that it would be classified as a TGA, rather than an EMA, based on the 2006 amendments to the Act. On February 27, 2007, a group of plaintiffs that included Nassau-Suffolk commenced this action to challenge HHS’s decision pursuant to § 702 of the Administrative Procedure Act (“APA”), 5 U.S.C. § 702.3 Plaintiffs ar*139gued that HHS had incorrectly classified Nassau-Suffolk as a TGA, and sought declaratory and injunctive relief directing the agency to return the entity to the EMA funding category. The district court denied plaintiffs’ application for a preliminary injunction on March 1, 2007. County of Nassau, N.Y. v. Leavitt, No. 07 Civ. 816, 2007 WL 708321, at *4 (E.D.N.Y. Mar. 1, 2007).
Following that decision, plaintiffs filed an interlocutory appeal with this Court, see 28 U.S.C. § 1292(a)(1), as well as a motion for an injunction pending appeal, see Fed. R.App. P. 8.4 We denied the motion for injunctive relief on May 4, 2007. Almost a year later, however, we reversed the district court and held that plaintiffs had established a likelihood of success on the merits of their claims. See Leavitt, 524 F.3d at 419.
On remand, HHS conceded that Nassau-Suffolk was to be funded as an EMA in FY 2009, but defendants moved to dismiss plaintiffs’ claims relating to FYs 2007 and 2008 as moot. Defendants’ argument was simple: no relief was available because HHS had distributed the funds that were appropriated by Congress for those fiscal years to other EMAs. The district court expressed concern about the “extreme consequences of holding that Plaintiffs’ claims for the 2007 and 2008 fiscal years are moot,” and it denied the motion without prejudice in order to examine whether HHS had, in fact, exhausted the appropriations for FYs 2007 and 2008.
Defendants then submitted an April 16, 2009 declaration from Douglas H. Morgan, the director of the HHS division that administers the grant program. The affidavit stated that, with respect to FYs 2007 and 2008, “[n]o remaining ... funds appropriated by Congress ... are available for obligation by HHS.” Based on that submission, the district court dismissed plaintiffs’ claims as moot, reasoning that it “lack[ed] authority” to “create ... special funding or re-organize their scheduled distributions for the upcoming years.”
II. DISCUSSION
We review de novo the district court’s conclusion that plaintiffs’ claims are moot. N.Y. Civil Liberties Union v. Grandeau, 528 F.3d 122, 128 (2d Cir.2008). On appeal, plaintiffs mount a two-front attack on the lower court’s decision. First, they argue that “the absence of funding did not absolve the government of its statutory obligations” under the Ryan White Act, and that the district court “still had the authority and power to enter a judgment declaring [defendants] liable for the additional Ryan White [Act] funds that should have been awarded” in FYs 2007 and 2008. Second, plaintiffs contend that the district court also erred by holding that they could not seek compensation from the appropriation created by the Judgment Fund, 31 U.S.C. § 1304(a). At bottom, however, both of these arguments fail to account for the limitations on this action resulting from the federal government’s sovereign immunity and the Appropriations Clause. Accordingly, for the reasons set forth below, we hold that plaintiffs’ claims are moot.
*140Article III of the Constitution limits federal courts’ authority — that is, our subject matter jurisdiction — to disputes involving “live cases and controversies.” United States v. Quattrone, 402 F.3d 304, 308 (2d Cir.2005). A number of justiciability doctrines govern the contours of this power; pertinent here is mootness, which concerns when and whether a case is “live.” Specifically, under the “general rule” of mootness, courts’ subject matter jurisdiction ceases when “an event occurs during the course of the proceedings or on appeal ‘that makes it impossible for the court to grant any effectual relief whatever to a prevailing party.’ ” Id. (quoting Church of Scientology v. United States, 506 U.S. 9, 12, 113 S.Ct. 447, 121 L.Ed.2d 313 (1992)).5
An understanding of why plaintiffs’ claims are moot requires an understanding of the scope of the relief that was available to them in the first instance in this action against HHS and federal employees in their official capacities. Absent an “unequivocally expressed” statutory waiver, the United States, its agencies, and its employees (when functioning in their official capacities) are immune from suit based on the principle of sovereign immunity. Dep’t of the Army v. Blue Fox, Inc., 525 U.S. 255, 260-61, 119 S.Ct. 687, 142 L.Ed.2d 718 (1999). “This may leave some aggrieved parties without relief, but that is inherent in the doctrine of sovereign immunity.” Adeleke v. United States, 355 F.3d 144, 150-51 (2d Cir.2004).
In this case, plaintiffs escaped this bar by invoking § 702 of the APA, 5 U.S.C. § 702, in which Congress enacted a limited waiver of the federal government’s sovereign immunity for claims of “legal wrong [sustained] because of agency action ... seeking relief other than money damages.” Id. The “agency action” plaintiffs challenge is HHS’s February 2007 decision to reclassify Nassau-Suffolk as a TGA under the 2006 amendments to the Ryan White Act, and they argue that they are legally entitled to funding as an EMA during FYs 2007 and 2008. And, as the district court understood, § 702 limited the scope of the available relief in such an action from its inception. Plaintiffs therefore could only seek relief “other than money damages.” Id. (emphasis added).6
In this regard, careful attention must be paid to the meaning of “money damages” in § 702. “The fact that a judicial remedy may require one party to pay money to another is not a sufficient reason to characterize the relief as ‘money damages.’ ” Bowen v. Massachusetts, 487 U.S. 879, 893, 108 S.Ct. 2722, 101 L.Ed.2d 749 (1988) (quoting 5 U.S.C. § 702). Rather, in this context, the term “money damages” refers to compensatory relief that functions as a substitute for lost property. See id. at 895, 108 S.Ct. 2722; see also Ward v. Brown, 22 F.3d 516, 520 (2d Cir.1994). 'Thus, “sovereign immunity bars [plaintiffs] from seeking [monetary] compensation” under § 702. Diaz v. United States, 517 F.3d 608, 612 (2d Cir.2008). As such, § 702 only functions as an effective *141waiver of the government’s sovereign immunity to the extent that plaintiffs seek to force HHS to return property to Nassau-Suffolk, where the res at issue is the funds appropriated by Congress for this grant program for FYs 2007 and 2008.
Analytically speaking, the fungibility often associated with money obscures, to some extent, the distinction between: (1) relief that seeks to compensate a plaintiff for a harm by providing a substitute for the loss, which is unavailable in an action under § 702; and (2) relief that requires a defendant to transfer a specific res to the plaintiff. See Diaz, 517 F.3d at 612. But where the object of a plaintiffs claims is the public fisc, the Appropriations Clause of the Constitution puts things in perspective: “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.” U.S. Const, art. I, § 9, cl. 7. In other words, “‘no money can be paid out of the Treasury unless it has been appropriated by an act of Congress.’ ” Office of Pers. Mgmt. v. Richmond, 496 U.S. 414, 424, 110 S.Ct. 2465, 110 L.Ed.2d 387 (1990) (quoting Cincinnati Soap Co. v. United States, 301 U.S. 308, 321, 57 S.Ct. 764, 81 L.Ed. 1122 (1937)). Thus, in cases challenging an agency’s expenditure of funds, the res at issue is identified by reference to the congressional appropriation that authorized the agency’s challenged expenditure. To seek funds from another source is to seek compensation rather than the specific property the plaintiff aims to recover. A claim seeking the former type of relief falls outside the scope of the waiver of sovereign immunity arising from § 702 of the APA.
To our knowledge, our sister Circuit in the District of Columbia is the only federal appellate court that has confronted this juxtaposition of sovereign immunity and the Appropriations Clause under the circumstances presented by this case.7 In City of Houston v. Department of Housing & Urban Development, 24 F.3d 1421 (D.C.Cir.1994), Houston challenged the decision of the Department of Housing and Urban Development (“HUD”) to reduce its FY 1986 community development block grant. Before Houston commenced the action, however, two events occurred: (1) HUD awarded the funds at issue to other grant recipients, thereby exhausting the relevant FY 1986 appropriation; and (2) the FY 1986 appropriation authorizing the grants expired and therefore lapsed.8 See id. at 1425. The D.C. Circuit held that *142these events served as “two independent grounds” for dismissing Houston’s claims. Id. at 1427. “[T]o avoid having its case mooted, a plaintiff must both file its suit before the relevant appropriation lapses and seek a preliminary injunction preventing the agency from disbursing those funds.” Id. (emphasis in original). The court reasoned that, when a litigant fails to take either step, “federal courts are without authority to provide monetary relief’ because the Appropriations Clause prevents additional funds from being paid out of the Treasury. Id. at 1428. It reasoned further that awarding “funds available from sources other than the 1986 appropriation” would contravene the “fundamental requirement” of § 702 of the APA “that a plaintiff seek relief ‘other than money damages. ’ ” Id. (emphasis in original) (quoting 5 U.S.C. § 702).
Under City of Houston, which we now follow, plaintiffs’ claims are moot. In so holding, we are mindful that, unlike in City of Houston, plaintiffs in this case sought to enjoin HHS’s expenditure of the funds for FYs 2007 and 2008 before HHS exhausted the relevant appropriations. Thus, whereas the City of Houston plaintiff could be faulted for failing to act, plaintiffs here took action but were unable to preserve the status quo. As a result, while the claims in City of Houston were moot at the time they were filed, plaintiffs’ claims became moot, despite their efforts, during the course of this litigation. Unfortunately, however, these are distinctions without a difference for purposes of the mootness doctrine. Although the City of Houston court indicated that a plaintiff must.“seek a preliminary injunction,” id. at 1427, its analysis applies with equal force where a plaintiff attempts, but ultimately fails, to enjoin an agency’s expenditures. Our analysis turns on the fact that, irrespective of the status of these appropriations when the action was commenced, HHS had exhausted them by the time the proceedings were remanded.9 After this was verified by the district court, the only option “remaining to the court [was] that of announcing the fact and dismissing the cause.” Ex parte McCardle, 74 U.S. (7 Wall.) 506, 514, 19 L.Ed. 264 (1868).
Plaintiffs seek to evade the holding of City of Houston by arguing that, notwithstanding HHS’s exhaustion of the appropriations at issue, their claims are not moot because they could collect on a judgment from the appropriation in the Judgment Fund, 31 U.S.C. § 1304(a). The Judgment Fund is a “permanent, indefinite appropriation for the payment of judgments.” GAO, 3 Principles, supra note 7, at 14-31. But the availability of this appropriation has limits. It “constitutes an appropriation of amounts sufficient to pay ‘final judgments ... and interest and *143costs,’ ” id. at 14-32, only when the sought-after payment is: (1) “not otherwise provided for” by law; (2) “certified by the Secretary of the Treasury”; and (3) payable under, inter alia, 28 U.S.C. § 2414 (relating to final judgments entered by federal district courts). 31 U.S.C. § 1304(a).
Moreover, the Judgment Fund does not waive the government’s sovereign immunity, and “the legal basis for a judgment or award must be found elsewhere in the law.” GAO, 3 Principles, at 14-34. As noted above, because plaintiffs rely on the government’s waiver of its sovereign immunity in § 702 of the APA, the only available remedy is an injunction directing HHS to fund Nassau-Suffolk as an EMA in FYs 2007 and 2008 from the appropriations that were authorized by Congress for those years. Money from the Judgment Fund, by contrast, would function as a substitute remedy to compensate plaintiffs for losses they suffered during FYs 2007 and 2008. Such a remedy would constitute “money damages” within the meaning of that term in § 702 of the APA, and the government has not waived its sovereign immunity with respect to such claims.10 In light of this immunity, the district court lacked authority to grant relief based on the Judgment Fund.
Finally, even if defendants had waived their immunity, the Judgment Fund’s appropriation would not be available because the statute’s first requirement — that the payment sought must not be “otherwise provided for,” 31 U.S.C. § 1304(a)(1) — is not satisfied. “There is only one proper source of funds in any given case.” GAO, 3 Principles, at 14^10. In this case, that source is the congressional appropriations for FYs 2007 and 2008 relating to Part A of the Ryan White Act. Where, as here, “payment of a particular judgment is otherwise provided for as a matter of law, the fact that the defendant agency has insufficient funds at that particular time does not operate to make the Judgment Fund available.” Id. at 14-39. We are persuaded by the GAO’s construction of the operative statutory phrase, and therefore conclude that the appropriations relating to the funds plaintiffs seek are “otherwise provided for,” 31 U.S.C. § 1304(a)(1). Consequently, insofar as the Judgment Fund is concerned, defendants are entitled to sovereign immunity and the statutory prerequisites for access to this appropriation are not satisfied. Therefore, we hold that this alternative appropriation is unavailable as a funding source for the remedy plaintiffs seek.
III. CONCLUSION
Defendants acknowledge that, based on our prior interpretation of the statute, see Leavitt, 524 F.3d at 414, HHS misapplied *144the Ryan White Act’s 2006 amendments to Nassau-Suffolk. There is no dispute that Nassau-Suffolk has now been properly funded as an EMA during FY 2009. There is also no dispute that, by the time this action was remanded to the district court, HHS had exhausted the congressional appropriations relating to FYs 2007 and 2008 of the Ryan White Act grant program. However, in light of defendants’ sovereign immunity and the Appropriations Clause, resort to those appropriations was the only remedy available to plaintiffs for their claims. We therefore hold that plaintiffs’ claims relating to FYs 2007 and 2008 are moot because no effectual relief may be granted.
Like the district court, we too are aware of the consequences of the result that we now announce. The principles that govern this appeal, however, stem from the very foundation of our institutional authority. As a court of limited jurisdiction, we are not free to exceed the bounds of the legal framework that governs our operation. Accordingly, we affirm the judgment of the district court dismissing plaintiffs’ claims.