19 CFR 12.30: Whaling.

The importation and exportation of whales or whale products taken or processed in violation of the International Convention for the Regulation of Whaling signed at Washington under date of December 2, 1946 (Publication No. 3383, Department of State, Whaling Convention), or of the Whaling Convention Act of 1949 (16 U.S.C. 916 through 916(1)), or of any regulation issued under the Act (50 CFR part 351) is unlawful. Customs officers and employees shall perform all functions required of them by the above-mentioned convention, law and regulation.