Search and Seizure in International Waters
Just a little info from the web site of the United States Coast Guard.
The specific statutory authority for the Coast Guard Law Enforcement mission is given in 14 USC 2, “The Coast Guard shall enforce or assist in the enforcement of all applicable laws on, under and over the high seas and waters subject to the jurisdiction of the United States.” In addition, 14 USC 89 provides the authority for U.S. Coast Guard active duty commissioned, warrant and petty officers to enforce applicable U.S. law. It authorizes Coast Guard personnel to enforce federal law on waters subject to U.S. jurisdiction and in international waters, as well as on all vessels subject to U.S. jurisdiction (including U.S., foreign and stateless vessels).
The only federal law enforcement agency with jurisdiction in both U.S. waters and on the high seas, the Coast Guard’s enforcement of U.S. laws and treaties focuses on conducting multi-agency counter-drug operations, interdicting illegal migrants and contraband, protecting living marine resources, maritime homeland security and helping to stem weapons proliferation, among other critical tasks.
See here for some current applicability of interdiction on the high seas.