46 U.S.C. § 70051

Whenever the President by proclamation or Executive order declares a national emergency to exist by reason of actual or threatened war, insurrection, or invasion, or disturbance or threatened disturbance of the international relations of the United States, or whenever the Attorney General determines that an actual or anticipated mass migration of aliens en route to, or arriving off the coast of, the United States presents urgent circumstances requiring an immediate Federal response, the Secretary of the department in which the Coast Guard is operating may make, subject to the approval of the President, rules and regulations governing the anchorage and movement of any vessel, foreign or domestic, in the territorial waters of the United States, may inspect such vessel at any time, place guards thereon, and, if necessary in his opinion in order to secure such vessels from damage or injury, or to prevent damage or injury to any harbor or waters of the United States, or to secure the observance of the rights and obligations of the United States, may take, by and with the consent of the President, for such purposes, full possession and control of such vessel and remove therefrom the officers and crew thereof and all other persons not specially authorized by him to go or remain on board thereof. Whenever the President finds that the security of the United States is endangered by reason of actual or threatened war, or invasion, or insurrection, or subversive activity, or cyber incidents, or transnational organized crime, or foreign state threats, or of disturbances or threatened disturbances of the international relations of the United States, the President is authorized to institute such measures and issue such rules and regulations— (a) to govern the anchorage and movement of any foreign-flag vessels in the territorial waters of the United States, to inspect such vessels at any time, to place guards thereon, and, if necessary in his opinion in order to secure such vessels from damage or injury, or to prevent damage or injury to any harbor or waters of the United States, or to secure the observance of rights and obligations of the United States, may take for such purposes full possession and control of such vessels and remove therefrom the officers and crew thereof, and all other persons not especially authorized by him to go or remain on board thereof; (b) to safeguard against destruction, loss, or injury from sabotage or other subversive acts, accidents, or other causes of similar nature, vessels, harbors, ports, and waterfront facilities in the United States and all territory and water, continental or insular, subject to the jurisdiction of the United States. The President may delegate the authority to issue such rules and regulations to the Secretary of the department in which the Coast Guard is operating. Any appropriation available to any of the Executive Departments shall be available to carry out the provisions of this subchapter.