Interstate Compacts — Agreements Between States

Interstate compacts are binding agreements between two or more states, authorized by the Compact Clause of the U.S. Constitution (Article I, Section 10, Clause 3), that create shared governance structures for problems that cross state borders. There are over 200 active interstate compacts governing everything from water allocation (the Colorado River Compact divides water among 7 states) to professional licensing (the Nurse Licensure Compact allows nurses to practice across state lines) to criminal justice (the Interstate Compact for Adult Offender Supervision manages probation and parole transfers). When Congress consents to a compact, it becomes federal law — enforceable in federal court and binding on member states even if future legislatures would prefer to withdraw. Interstate compacts are one of the oldest and most consequential tools of American federalism, predating the Constitution itself.

Current Law (2026)

Legal Authority

• Article I, Section 10, Clause 3 — Compact Clause ("No State shall, without the Consent of Congress...enter into any Agreement or Compact with another State") — establishes the constitutional framework for interstate compacts
• 4 U.S.C. § 112 — Compacts between States for cooperation in prevention and punishment of crime (requires interstate crime compacts to be filed with and published by appropriate state departments)
• Individual compact statutes — Each Congressionally-consented compact is enacted as a separate federal statute (e.g., the Delaware River Basin Compact Act, the Multistate Tax Compact, the Interstate Compact for Juveniles)

How It Works

The Compact Clause prohibits states from entering agreements without Congressional consent — but the Supreme Court has interpreted this narrowly. In Virginia v. Tennessee (1893) and U.S. Steel Corp. v. Multistate Tax Commission (1978), the Court held that Congressional consent is required only when a compact increases state power at the expense of federal authority or encroaches upon federal supremacy; boundary settlements, cooperative law enforcement arrangements, and mutual aid agreements operate without formal consent because they don't affect the federal balance of power. When Congress does consent, the compact becomes federal law under the Supremacy Clause. Compact formation follows a common pattern: states identify a shared governance problem, negotiate terms (often through the Council of State Governments), each state legislature enacts the identical compact text as state law, Congress enacts it if consent is required, and a compact commission is created to administer programs — a multi-year process threading through multiple legislatures with different political dynamics.

Compact commissions are the administrative workhorses. Most compacts create quasi-governmental bodies — staffed by commissioners appointed by member states — that administer the compact's programs, adopt rules, resolve disputes, and enforce compliance. Examples include the Delaware River Basin Commission (manages water resources across 4 states), the Port Authority of New York and New Jersey (operates airports, bridges, tunnels, and transit), and the Interstate Commission for Adult Offender Supervision (manages transfer of probationers and parolees across state lines). These commissions exercise real governmental power — rulemaking, enforcement, and sometimes taxation — but are accountable to member states rather than any single state or the federal government.

Compact subjects span a wide range of shared governance needs:

• Water allocation: The oldest and most consequential category. The Colorado River Compact (1922), Rio Grande Compact, Delaware River Basin Compact, and dozens of others divide shared water resources among states with competing needs.
• Professional licensing: The Nurse Licensure Compact, Psychology Interjurisdictional Compact, Physical Therapy Compact, and others allow licensed professionals to practice across state lines without obtaining separate licenses in each state — addressing workforce mobility in healthcare and other fields.
• Criminal justice: The Interstate Compact for Adult Offender Supervision (all 50 states), Interstate Compact for Juveniles, and Interstate Agreement on Detainers govern the transfer of offenders, juveniles, and prisoners across state lines.
• Transportation: Port authorities, bridge commissions, and regional transit compacts coordinate infrastructure that crosses state boundaries.
• Environment: Regional compacts address air quality (Ozone Transport Commission), hazardous waste (regional disposal compacts), and shared ecosystems.
• Education: The Interstate Compact on Educational Opportunity for Military Children (all 50 states) ensures smooth school transitions for children of military families.

Most compacts allow member states to withdraw with 1–2 years' notice, but withdrawal doesn't retroactively eliminate obligations incurred during membership. Disputes between member states over compact interpretation are resolved in federal court for Congressionally-consented compacts, or through the compact commission's own dispute resolution process; the Supreme Court has original jurisdiction over disputes between states, including compact disputes.

How It Affects You

If you're a licensed professional considering multi-state practice or relocation: Interstate licensing compacts have eliminated the biggest friction point in professional mobility for many healthcare and education professions. The Nurse Licensure Compact (NLC) — the most widely adopted, covering 40+ states — allows registered nurses to practice in any member state under a single multistate license. The Interstate Medical Licensure Compact (IMLC) streamlines — but does not eliminate — the physician licensing process in member states; you still need a license in each state but can get them faster (weeks vs. months). The Psychology Interjurisdictional Compact (PSYPACT) allows licensed psychologists to practice telepsychology across member states. The Teacher Interstate Compact — adopted but not yet universally implemented — would allow reciprocal teacher certification. If you're a nurse: check the NLC map at ncsbn.org/nurse-licensure-compact.htm — if your home state is a compact member, your license is already multistate. If you're a physician applying for licenses in multiple states: check the IMLC portal at imlcc.org for participating states and the streamlined application process. If you're a physical therapist, occupational therapist, speech-language pathologist, or other licensed healthcare professional: check whether your profession has an active compact at licenseportability.org, maintained by the Council of State Governments.

If you're a military family facing a PCS relocation: The Interstate Compact on Educational Opportunity for Military Children (formally called the Military Interstate Children's Compact Commission, or MIC3) operates in all 50 states + DC — it is one of the most universally adopted compacts in the U.S. It guarantees that when your family receives PCS orders: your children's academic records transfer seamlessly; enrollment deadlines and residency requirements cannot block immediate enrollment; course placement cannot be disrupted by curriculum differences between states; students within 60 days of high school graduation are allowed to graduate even if the new school's requirements differ; extracurricular activities and sports eligibility is maintained. If a school district is not following the compact's requirements, contact your installation's School Liaison Officer (SLO) — every installation has one, and they have authority to escalate compact compliance issues. The MIC3 website (mic3.net) includes a complaint resolution process and contact information for each state's compact commissioner. For professional license portability for military spouses, many states have enacted separate expedited licensing laws; check militaryonesource.mil/education-employment/for-spouses for current state-by-state status.

If you're on probation or parole and need to move to another state: The Interstate Compact for Adult Offender Supervision (ICAOS) governs every interstate transfer of supervision — you cannot simply move to another state while on probation or parole without going through the compact process. The process starts with your supervising officer filing an application; the receiving state has 45 business days to accept or reject the transfer. The receiving state can impose its own supervision conditions (which may be more restrictive than your current state), and it takes over enforcement. Common transfer denial reasons: the receiving state doesn't have jurisdiction over a sex offender with your conviction type; you don't have a verified residence or employment plan; the receiving state's caseload is at capacity. If you have a compelling reason to transfer (family caregiver obligations, verified job offer, medical treatment), document these in your transfer application — they are weighed in the acceptance decision. Transfers for domestic violence situations with safety concerns have special provisions. The ICAOS rules and state contact directory are at interstatecompact.org. If your transfer is denied and you believe it was improper, the compact has a formal dispute resolution process through your probation/parole officer and the state compact administrator.

If you're a western water user, farmer, or municipal water manager: Interstate water compacts are the legal foundation of western water law — and they determine how much water your state has available to allocate. The Colorado River Compact (1922) divides the river between the Upper (Colorado, Wyoming, Utah, New Mexico) and Lower (California, Arizona, Nevada) basin states; the allocation of 7.5 million acre-feet per basin per year was based on 1920s flow measurements that have proven too optimistic, creating the chronic over-appropriation that drives today's crisis. Current (2026) negotiations to replace the 2007 Interim Guidelines are among the most consequential water law proceedings in U.S. history — your state's water district and congressional delegation are the right channels for input. Other critical water compacts include the Republican River Compact (Kansas/Nebraska/Colorado), Rio Grande Compact, and numerous smaller basin agreements. If your agricultural water rights depend on compact-allocated supplies from a shared river, your state engineer's office tracks compact call accounting — the mechanism by which upstream states must curtail deliveries when downstream compact obligations aren't being met. Water attorneys and state water agencies are essential resources for navigating compact implications on specific water rights; the Western States Water Council (westernstateswater.org) tracks compact status and litigation across the region.

State Variations

Interstate compacts are inherently about state-to-state variation and coordination:

• Not all states are members of all compacts — participation is voluntary (with some exceptions where federal law effectively requires participation)
• State implementing legislation may vary even when compact text is identical, depending on how each state structures its participation
• Compact commissions may adopt rules that apply differently across member states based on local conditions
• Some compacts (like the National Popular Vote Interstate Compact) are politically controversial and have divided state legislatures along partisan lines
• States may belong to regional compacts (New England, Southern, Western) that address region-specific issues

Implementing Regulations

Interstate compacts are agreements between states ratified under the Compact Clause (U.S. Const. Art. I, § 10, cl. 3). Compacts with federal participation are codified in the U.S. Code and their implementing regulations appear in the CFR. One notable example:

• 18 CFR Part 806 — Review and Approval of Projects (Susquehanna River Basin Commission — SRBC) (implementing the Susquehanna River Basin Compact, enacted by Congress at Pub. L. 91-575 (1970), under which the federal government (represented by the Army Corps of Engineers) is a co-signatory alongside Pennsylvania, New York, and Maryland; the SRBC reviews and approves water withdrawals, consumptive uses, and diversions in the Susquehanna River Basin, which drains 43% of New York and 61% of Pennsylvania before entering the Chesapeake Bay):

  • § 806.4 — Projects subject to review: any project that withdraws surface water or groundwater from the Susquehanna River Basin in excess of an average of 100,000 gallons per day (gpd) over any 30-day period must apply for SRBC approval before commencing operations; projects below this threshold are subject to registration but not formal approval; the 100,000 gpd threshold captures all major industrial, municipal, power generation, and agricultural withdrawals in the Basin
  • § 806.5 — Consumptive use projects: projects that consumptively use (withdraw and not return) water in excess of 20,000 gpd average over any 30-day period require SRBC review; consumptive use is separately regulated from withdrawal because it represents a permanent reduction in the Basin's water budget — water that is evaporated, incorporated into products, or transported out of the watershed doesn't return to the river system; this threshold was central to SRBC oversight of Marcellus Shale natural gas hydraulic fracturing operations in Pennsylvania, which require large water volumes for fracking fluid
  • § 806.6 — Diversions: projects that divert water into or out of the Susquehanna River Basin require SRBC approval regardless of volume; diversions between river basins are a particular concern for long-term basin water budgets — the Great Lakes Compact and Delaware River Basin Commission have parallel diversion controls
  • § 806.12 — Hydrogeologic evaluation: groundwater withdrawal projects require a hydrogeologic evaluation, which may include an aquifer test to characterize the aquifer's yield capacity and potential impacts on neighboring wells; the evaluation must demonstrate that the proposed withdrawal will not cause significant adverse impacts to nearby surface waters (stream baseflow), other groundwater users, or protected ecological resources; SRBC staff review the hydrogeologic evaluation and may require additional testing or analysis
  • § 806.22 — Standards for water conservation: all approved water use projects must implement water conservation measures; SRBC has adopted water conservation standards that approved projects must demonstrate compliance with — covering metering, loss reduction, and efficiency measures appropriate to the project type

  The Susquehanna River Basin Commission gained national attention during the Marcellus Shale natural gas boom (approximately 2008–2016), when hydraulic fracturing operations in Pennsylvania and southern New York required massive water withdrawals — typically 3–5 million gallons per fracking well — triggering SRBC review. SRBC approved water withdrawals for natural gas drilling under conditions requiring low-flow protections (withdrawals suspended when stream flows drop below SRBC-established minimum pass-by flows) and surface water mitigation fees. The SRBC model — a multi-state, federal-state compact commission with binding permit authority — is distinct from the more advisory function of most water resource bodies. The Delaware River Basin Commission (DRBC) operates under a parallel structure covering the Delaware River watershed, and together they provide comprehensive multi-state oversight of the two river systems that drain most of the Mid-Atlantic region.

Pending Legislation

No standalone interstate compact reform bills have been introduced in the 119th Congress. Individual compacts (e.g., driver's license compacts, emergency management compacts) are addressed in topic-specific legislation.

Recent Developments

Interstate licensing compacts have expanded rapidly, driven by the COVID-19 pandemic's demonstration that telehealth and remote work require professionals to be licensed across state lines. The Nurse Licensure Compact now includes nearly 40 member states, and new compacts for counselors, social workers, and other professions are being developed. The National Popular Vote Interstate Compact — an agreement to award each member state's electoral votes to the national popular vote winner — has been enacted by 17 states and DC (representing 209 electoral votes as of 2026, short of the 270 needed to take effect) and remains among the most politically significant compact proposals. Water compacts continue to be renegotiated as climate change alters river flows — the Colorado River Compact's century-old allocation framework is under intense pressure as the river delivers less water than was assumed when the compact was written.