Commissioned, warrant, and petty officers of the Coast Guard are deemed to be officers of the customs and when so acting shall, insofar as performance of the duties relating to customs laws are concerned, be subject to regulations issued by the Secretary of the Treasury governing officers of the customs.
14 U.S. Code § 143 - Treasury Department
This section will not repeal the sections cited above, but makes further provision that Coast Guard personnel when acting as officers of the customs shall, insofar as enforcing customs laws are concerned, be subject to regulations governing regular officers of the customs. 81st Congress, House Report No. 557.