10 USC 5013a - Secretary of the Navy: powers with respect to Coast Guard

(a) Whenever the Coast Guard operates as a service in the Navy under section 3 of title 14, the Secretary of the Navy has the same powers and duties with respect to the Coast Guard as the Secretary of Homeland Security has when the Coast Guard is not so operating.
(b) While operating as a service in the Navy, the Coast Guard is subject to the orders of the Secretary of the Navy, who may order changes in Coast Guard operations to make them uniform, to the extent he considers advisable, with Navy operations.