Captain of the Port, as used in this part, means the officer of the Coast Guard, under the command of a District Commander, so designated by the Commandant for the purpose of giving immediate direction to Coast Guard law enforcement activities within the Captain of the Port's assigned area. In addition, the District Commander will be Captain of the Port with respect to the remaining areas in the District not assigned to officers designated by the Commandant as Captain of the Port.
33 C.F.R. §6.01-3