Interstate compacts allow individual states to maintain consistency in their laws by coordinating on a multistate level. While they may not rival the power of the federal government, compacts may be a next-best option for states facing sudden cutbacks in support from Washington, D.C. States could use them to preserve ACA-initiated programs, or create new systems from scratch.

There are currently over 200 active interstate compacts, many of which are regional. Twenty-two agreements are national in scope, and each one addresses a different issue facing the states. The Interstate Compact for Adult Offender Supervision, for example, oversees the transfer of parole and probation between states. And the Gulf States Marine Fisheries Commission is one of roughly two dozen water-related compacts that govern everything from fish stocks to the fair use of river basins by adjoining states.

Agencies that monitor compacts have authority, delegated from the states, to generate revenue and engage in rule-making—that is, they can create regulations to enforce the powers granted by a given compact. The Port Authority of New York and New Jersey, the Delaware River Port Authority, and the Washington Metro Area Transit Authority are all interstate-compact agencies that run rapid-transit systems.

There are constitutional limitations on these agreements, even though some actually predate the Constitution and were used to settle land disputes between the colonies. But states can largely work around those constraints.

The Compacts Clause of the Constitution—Article I, Section 10—says, “No State shall, without the Consent of Congress … enter into any Agreement or Compact with another State.” Despite that limiting language, states have regularly entered into these agreements without lawmakers’ approval at all, and the Supreme Court has supported them, curbing the scope of federal involvement in the process. In 1893, the Supreme Court ruled that the federal government’s authority to approve such agreements was only applicable when an agreement “may encroach upon or interfere with the just supremacy of the United States.” It was not completely clear what constraints this left on the states.

Nearly a century later, the Court took up the issue again, building on their earlier ruling in U.S. Steel Corporation v. Multistate Tax Commission in 1978. The Court found that the commission’s policies, which were intended to reform state taxation of multistate businesses, could have been enacted individually by each state. As a result, the Court ruled that the Multistate Tax Compact did not require the consent of Congress. To date, the test for when states need approval remains murky, but in general, when states enact programs they each could have done on their own, congressional approval is not necessary.