IIRC, an interstate compact requires Cogressional approval.
“. Article I, Section 10 of the United States Constitution provides that “No State shall, without the Consent of Congress... enter into any Agreement or Compact with another State.” Consent can be obtained in one of three ways. First, there can be a model compact and Congress can grant automatic approval for any state wishing to join it, such as the Driver License Compact. Second, states can submit a compact to Congress prior to entering into the compact. Third, states can agree to a compact then submit it to Congress for approval, which, if it does so, causes it to come into effect. Not all compacts between states require explicit Congressional approval – the Supreme Court ruled in Virginia v. Tennessee that only those agreements which would increase the power of states at the expense of the federal government required it.”