An interstate compact is a legally binding agreement between two or more states, and with congressional consent it operates like federal law for its members. The Constitution requires that approval for compacts that affect federal power, and Congress has consented to more than 200 of them. As of 2026 every state belongs to at least one compact, and some of the oldest — the Port Authority of New York and New Jersey, chartered in 1921, and the Colorado River Compact of 1922 — still run the infrastructure and water sharing they were created to manage. Compacts are how states coordinate when a problem crosses their borders and Congress has not preempted the field.
Where does the power to form compacts come from?
Article I, Section 10 of the Constitution says no state shall enter any agreement or compact with another state without the consent of Congress. Before that clause existed under the Articles of Confederation, states struck border and navigation deals freely, sometimes at each other's expense. The Supreme Court has read the modern clause to require consent mainly when a compact encroaches on federal supremacy; a simple boundary line may not need it, while anything creating a joint agency usually does. Congress grants consent through a statute that often approves the compact text itself or sets conditions the states must meet.
What do compacts actually govern?
The range is wide. Water allocation: the Colorado River Compact divides the river among seven western states, and the Rio Grande, Delaware, and Susquehanna basins run under their own compacts with federal commissioners. Transportation and infrastructure: the Port Authority of New York and New Jersey operates bridges, tunnels, airports, and seaports for both states as a single agency. Record sharing: the Driver License Compact lets member states exchange traffic violation and license data, so a suspension in one state follows a driver home. Corrections: the Interstate Compact for Adult Offender Supervision governs how parole and probation transfer between states, and a juvenile version does the same. Emergency management, education, and tax administration compacts fill other gaps.
How is a compact created and enforced?
| Step | Who acts |
|---|---|
| States negotiate and adopt identical text | State legislatures |
| Congress grants consent, with conditions if any | Congress |
| States ratify the consented text | State legislatures or governors |
| Joint commission or agency begins operating | Compact commission |
| Disputes resolved by commission rules or federal courts | Member states, courts |
Once consented and adopted, a compact binds member states under the Supremacy Clause — a state cannot repeal its way out unilaterally, and withdrawing usually requires the compact's own exit terms or fresh congressional consent. Enforcement runs through the compact's commission, and disputes between states go to federal courts, including the Supreme Court in original jurisdiction cases between states. Commissions can adopt binding rules and levy assessments on members, and the Supreme Court upheld that rulemaking power in the 1978 case reviewing the Delaware River Basin Commission.
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Who runs a compact day to day?
Most compacts establish an administrative commission with commissioners from each member state — often state officials by statute — and sometimes federal representatives for water and basin compacts. The Port Authority, one of the largest, is run by appointees of the two governors with professional staff operating facilities and issuing its own bonds. Smaller compacts run on lean staffs housed at a university center or a member agency. Commissions adopt bylaws, set budgets, collect dues, and can adopt rules that carry the force of law in member states, which is the feature that makes compacts more than treaties of intent.
What are the limits of compacts?
A compact cannot give states power the states do not have, and it cannot override federal law. Congress can impose and enforce conditions on consent, and federal agencies have refused consent to compacts they viewed as intruding on national policy. Withdrawal is hard by design, so compacts age: the Colorado River Compact's allocations, negotiated when the river's flow was overestimated, have caused decades of shortage disputes that the compact framework has had to absorb rather than solve. And new members must adopt identical text, which makes multistate compacts slow to amend — every state legislature must act.
Are new compacts still being formed?
Yes, though the pace is slow because every member legislature must adopt identical text. Recent decades produced the Interstate Medical Licensure Compact, which speeds physician licensing across member states, and nursing, emergency medical services, and occupational therapy compacts that work the same way for other professions. Psychology and counseling compacts followed in the late 2010s and early 2020s. These professional licensing compacts share a design: a member state treats out-of-state licensees as if locally licensed, with a data system to track discipline. Their spread shows the current direction of the tool — less about shared infrastructure and more about mutual recognition, letting workers move across state lines without restarting a licensing process in each one.
Why does this tool matter to ordinary residents?
Compacts decide practical things: whether your driver record follows you across a state line, how a probationer moves for a job, whose agencies regulate a shared river during a drought, and who runs the airport you fly from. When a compact commission holds a hearing or a member state proposes a compact rule change, the public comment process is the state's own — compacts add a layer of governance that most residents never see, but whose rules carry legal force across every member state at once.