2 U.S.C. § 2183: Protection of buildings and property

The Sergeants at Arms of the Senate and of the House of Representatives are authorized to make such regulations as they may deem necessary for preserving the peace and securing the Capitol from defacement, and for the protection of the public property therein, and they shall have power to arrest and detain any person violating such regulations, until such person can be brought before the proper authorities for trial.