19 U.S. Code § 1529 - Collection of fees on behalf of other agencies
The Customs Service shall be reimbursed from the fees collected for the cost and expense, administrative and otherwise, incurred in collecting any fees on behalf of any government  agency for any reason.
 So in original. Probably should be capitalized.
For transfer of functions, personnel, assets, and liabilities of the United States Customs Service of the Department of the Treasury, including functions of the Secretary of the Treasury relating thereto, to the Secretary of Homeland Security, and for treatment of related references, see sections 203(1), 551(d), 552(d), and 557 of Title 6, Domestic Security, and the Department of Homeland Security Reorganization Plan of November 25, 2002, as modified, set out as a note under section 542 of Title 6. For establishment of U.S. Customs and Border Protection in the Department of Homeland Security, treated as if included in Pub. L. 107–296 as of Nov. 25, 2002, see section 211 of Title 6, as amended generally by Pub. L. 114–125, and section 802(b) of Pub. L. 114–125, set out as a note under section 211 of Title 6.