Hmm makes me wounder about thier authority on NON u.s. boats and non u.s. persons. Looked around and found this, but am still woundering....
THE U.S. COAST GUARD
The U.S. Coast Guard is authorized to enforce, or assist in the enforcement of, all U.S. Federal laws applicable on, over, and under the high seas and waters subject to the jurisdiction of the United States. These include laws which provide for the U.S. Coast Guard to exclusively act, and those which the Coast Guard enforces primarily for some other Federal agency. Generally, the Coast Guard must determine on a case-by-case basis whether it has jurisdiction. Besides determining whether it has the domestic authority to assert jurisdiction, it often must also determine whether an assertion of jurisdiction is consistent with international law. In many cases involving a foreign vessel, the Coast Guard decides whether it has jurisdiction over the vessel and its personnel based on three elements: the activities of the vessel and personnel, the location of the vessel, and the nationality of the vessel.
Two notes are warranted here. The first relates to the phrase "waters subject to United States jurisdiction." This phrase encompasses more than United States territorial waters; it also extends to those waters where the United States, pursuant to an agreement with a foreign government, has been authorized to take law enforcement action involving United States or foreign vessels. Such waters could, and in actual practice do, include foreign territorial waters.
The second point is that the Coast Guard may go aboard any United States vessel at any time, anywhere to conduct a documentation and safety inspection. A search of a U.S. vessel beyond this type of inspection is subject to limitations under the United States Constitution. If a search extends beyond this narrowly defined scope, a court may be asked to evaluate the legality of the search by balancing the individual’s right to privacy in the specific circumstances of the search against society’s interest in detecting criminal conduct.