2 U.S.C. § 143c

In addition to amounts transferred pursuant to section 182b(e)(2) of this title, the Librarian of Congress may transfer amounts made available for salaries and expenses of the Library of Congress during a fiscal year to the applicable appropriations accounts of the United States Capitol Police in order to reimburse the Capitol Police for services provided in connection with a special event or program described in section 182b(a)(4) of this title.