D.C. Code § 10-503.19
The Capitol Police shall police the United States Capitol Buildings and Grounds under the direction of the Capitol Police Board, consisting of the Sergeant at Arms of the United States Senate, the Sergeant at Arms of the House of Representatives, and the Architect of the Capitol, and shall have the power to enforce the provisions of this part, and regulations promulgated under § 10-503.25 and to make arrests within the United States Capitol Buildings and Grounds for any violations of any law of the United States, of the District of Columbia, or of any State, or any regulation promulgated pursuant thereto; provided, that for the fiscal year for which appropriations are made by this Act, the Capitol Police shall have the additional authority to make arrests within the District of Columbia for crimes of violence, as defined in 18 U.S.C. § 16, committed within the Capitol Buildings and Grounds and shall have the additional authority to make arrests, without a warrant, for crimes of violence, as defined in 18 U.S.C. § 16, committed in the presence of any member of the Capitol Police performing official duties; provided further, that the Metropolitan Police force of the District of Columbia are authorized to make arrests within the United States Capitol Buildings and Grounds for any violation of any such laws or regulations, but such authority shall not be construed as authorizing the Metropolitan Police force, except with the consent or upon the request of the Capitol Police Board, to enter such buildings to make arrests in response to complaints or to serve warrants or to patrol the United States Capitol Buildings and Grounds. For the purpose of this section, the word "grounds" shall include the House Office Buildings parking areas and that part or parts of property which have been or hereafter are acquired in the District of Columbia by the Architect of the Capitol, or by an officer of the Senate or the House, by lease, purchase, intergovernment transfer, or otherwise, for the use of the Senate, the House, or the Architect of the Capitol.
D.C. Code § 10-503.19
Concurrent jurisdiction over Office of Technology Assessment: Act of November 14, 1977, 91 Stat. 1362, Pub. L. 95-175, provided that the supervision of the United States Capitol Police shall extend over that part or parts of the premises leased by the Office of Technology Assessment. In carrying out such supervision, the United States Capitol Police shall have concurrent jurisdiction with that of the Metropolitan Police of the District of Columbia.