Unfortunately, the Constitution (Article 1 Section 10) forbids states from entering into alliances and treaties with other countries, or with one another, without the explicit permission of Congress.
Which amendment contains the clause claiming the rest of the contract survives if parts are just unilaterally deleted by one side?
The Posse Comitatus Act makes it a criminal statute that bars anyone from willfully using federal military forces — the Army, Navy, Marine Corps, Air Force, and Space Force — "to execute the laws" unless expressly authorized by the Constitution or an act of Congress.