Where state law and a Compact conflict, courts are required under the Supremacy Clause (for Compacts with consent) and as a matter of contract law to apply the terms and conditions of the Compact to a given case. The fact that a judge may not like the effect of a Compact or believes that other state laws can produce a more desirable outcome is irrelevant. The Compact controls over individual state law and must be given full force and effect by the courts. For a full discussion of giving Compacts effect over conflicting state law, see BUENGER, ET AL., supra, at 54–66.

Many Compacts are silent about how states may apply their own state law. In cases involving such Compacts, courts use different analyses that generally reach the same holding. For example, the Ninth Circuit held that states may not apply state law unless the specific state law to be applied is specifically preserved in the Compact. Seattle Master Builders Ass’n v. Pac. Nw. Elec. Power & Conserv. Planning Council, 786 F.2d 1359, 1364 (9th Cir. 1986). Similarly, states do not have the unilateral right to exercise a veto over actions of an interstate commission created by a Compact:

[W]hen enacted, a Compact constitutes not only law, but a contract which may not be amended, modified, or otherwise altered without the consent of all parties. It, therefore, appears settled that one party may not enact legislation which would impose burdens upon the Compact absent the concurrence of the other signatories. C. T. Hellmuth & Assocs., Inc. v. Washington Metro. Area Transit Auth., 414 F. Supp. 408, 409 (D. Md. 1976).

Some Compacts with just two or a few member states specifically allow states to apply new state law to a Compact provided that the other member states concur with applying that law. Most courts reason that the concurrence of other member states occurs when all of the states enact substantively identical law and express an intent that the law applies to a specific Compact. E.g., Int’l Union of Operating Eng’rs, Local 542 v. Delaware River Joint Toll Bridge Comm’n, 311 F.3d 273 (3d Cir. 2002) (citing cases and also noting New Jersey state courts use a less demanding analysis).

Occasionally, courts invoke the Contracts Clause of the U.S. Constitution in analyzing whether a state may apply its own law to a Compact. See, e.g., U.S. Trust Co. v. New Jersey, 431 U.S. 1, 32 (1977). Some courts use a contractual analysis without reference to the Contracts Clause of the federal or any state constitution. E.g., McComb v. Wambaugh, 934 F.2d 474, 479 (3d Cir. 1991). (“Having entered into a contract, a participant state may not unilaterally change its terms. A Compact also takes precedence over statutory law in member states.”).

By entering into a Compact, the member states contractually agree that the terms and conditions of the Compact supersede parochial state considerations. In effect, Compacts create collective governing tools to address multilateral issues and, as such, they govern the multilateral contingent on the collective will of the member states, not the will of any single member state. This point is critically important to the success and uniform application of the ICAOS. Compacts are ultimately more successful when states enact statutes and regulations to support them.