Congressional consent can significantly change the nature of an interstate Compact. “[W]here Congress has authorized the States to enter into a cooperative agreement, and where the subject matter of that agreement is an appropriate subject for congressional legislation, the consent of Congress transforms the States’ agreement into federal law under the Compact Clause.” Cuyler v. Adams, 449 U.S. 433, 440 (1981). Although most clearly articulated in Cuyler v. Adams, the rule that congressional consent transforms the states’ agreement into federal law has been recognized since 1852. See id. at 438 n.7.

As federal law, disputes involving the application or interpretation of an interstate Compact with congressional consent may be brought in federal court under 28 U.S.C. § 1331 (federal question jurisdiction), except where a Compact specifically authorizes suit only in state court. Federal court jurisdiction is not exclusive; under the Supremacy Clause of the U.S. Constitution, state courts, similar to federal counterparts, have the same obligation to give force and effect to the provisions of a congressionally approved Compact. The U.S. Supreme Court retains the final word on the interpretation and application of congressionally approved Compacts no matter whether the case arises in federal or state court. Delaware River Joint Toll Bridge Comm’n v. Colburn, 310 U.S. 419, 427 (1940) (“[T]he construction of such a [bi-state] Compact sanctioned by Congress by virtue of Article I, § 10, Clause 3 of the Constitution, involves a federal ‘title, right, privilege or immunity,’ which when ‘specially set up and claimed’ in a state court may be reviewed here on certiorari under § 237(b) of the Judicial Code.”).

Courts apply the Supremacy Clause when there is a conflict between an interstate Compact with consent and state law or state constitutions. See, e.g., Hinderlider v. La Plata River & Cherry Ditch Co., 304 U.S. 92, 108 (1938) (holding that states may, with congressional consent, enact Compacts even if those Compacts would conflict with rights granted under a state constitution); Wash. Metro. Area Transit Auth. v. One Parcel of Land, 706 F.2d 1312 (4th Cir. 1983) (Maryland may confer on an interstate agency federal quick-take condemnation powers not available to state agencies under Maryland’s constitution); Jacobson v. Tahoe Reg’l Planning Agency, 566 F.2d 1353, 1358 (9th Cir. 1977) (holding that “causes of action based on state constitutional provisions must fail because the Compact, as federal law, preempts state law.”); Frontier Ditch Co. v. Se. Colo. Water Cons. Dist., 761 P.2d 1117, 1124 (Colo. 1998) (concluding, “Thus, to the extent that there might be some arguable conflict between [the Compact’s] Article VI B’s grant of exclusive jurisdiction to Kansas and the Colorado water court’s jurisdiction [granted in that state’s constitution], Article VI B is the supreme law of the land and governs the rights of the parties in this case.”).

Courts also construe Compacts with consent under federal law, use federal law methods for interpreting the Compact and reviewing interstate commission interpretations and applications of the Compact. See, e.g., Carchman v. Nash, 473 U.S. 716, 719 (1985); League to Save Lake Tahoe v. Tahoe Reg’l Planning Agency, 507 F.2d 517, 521-25 (9th Cir. 1974) (“[A] congressionally sanctioned interstate Compact within the Compact Clause is a federal law subject to federal construction”); Friends of the Columbia Gorge v. Columbia River Gorge Comm’n, 213 P.3d 1164, 1170–74, 1189 (Or. 2009) (applying the federal Chevron method for reviewing the interstate Commission’s interpretation of federal law granting consent to the Compact, and the federal Auer method for reviewing the interstate Commission’s interpretation of its own administrative rules).

Consent can also make federal remedies available for violations of a Compact. For example, the Interstate Agreement on Detainers (to which the United States is also a signatory) is considered a law of the United States; a violation of which is grounds for habeas corpus relief under 28 U.S.C. § 2254. See, e.g., Bush v. Muncy, 659 F.2d 402, 407 (4th Cir. 1981), cert. denied, 455 U.S. 910 (1982).

Finally, unrelated to the federal law character of a Compact with consent, Congress can use the consent process to alter substantively the application of federal law in Compact situations. See, e.g., McKenna v. Wash. Metro. Area Transit Auth., 829 F.2d 186, 188–89 (D.C. Cir. 1987) (Congress’ consent to Title III of the Washington Metropolitan Area Transit Regulation Compact effectively altered the application of the Federal Employers’ Liability Act to the Washington Metropolitan Area Transit Authority and exempted it from liability under that act).