D.C. Code § 10-503.22
In order to admit of the due observance within the United States Capitol Grounds of occasions of national interest becoming the cognizance and entertainment of Congress, the President of the Senate and the Speaker of the House of Representatives, acting concurrently, are hereby authorized to suspend for such proper occasions so much of the prohibitions contained in §§ 10-503.12 to 10-503.17 as would prevent the use of the roads and walks of the said grounds by processions or assemblages, and the use upon them of suitable decorations, music, addresses, and ceremonies; provided, that responsible officers shall have been appointed, and arrangements determined which are adequate, in the judgment of said President of the Senate and Speaker of the House of Representatives, for the maintenance of suitable order and decorum in the proceedings, and for guarding the Capitol and its grounds from injury.
D.C. Code § 10-503.22