Interstate Compacts

Article I, Section 10 provides that no state shall, without the consent of Congress, enter into any agreement or compact with another state or with a foreign power. The framers kept a practice from colonial and Confederation times, when colonies settled boundary disputes by agreement, while guarding against alliances that could threaten the union. In Virginia v. Tennessee in 1893 the Supreme Court held that congressional consent is required only for compacts that increase the political power of the states in ways that could encroach on federal authority, so many agreements take effect without it.

Compacts became a major tool of government in the twentieth century. New York and New Jersey created the Port Authority by compact in 1921, and seven states divided the waters of the Colorado River in the Colorado River Compact of 1922. Others created the Washington Metropolitan Area Transit Authority, regional river basin commissions, and agreements on driver licenses, parolees, the placement of children, and the licensing of nurses and other professionals. More than 200 compacts are in force, and a compact approved by Congress is treated as federal law.

Compacts are enforceable contracts, and disputes between states over them go directly to the Supreme Court, which has heard many water cases, including the long-running Rio Grande dispute among Texas, New Mexico, and Colorado. The National Popular Vote Interstate Compact, under which member states pledge their electoral votes to the national popular vote winner once states with a majority of electoral votes join, has drawn debate. Supporters see compacts as flexible cooperation without federal mandates, while critics say some compacts create agencies with weak public accountability.