Replies

US Code Title 40 Subtitle II Chapter 51 Section 5104

Unlawful acts
(2) Violent entry and disorderly conduct.— An individual or group of individuals may not willfully and knowingly—
(A) enter or remain on the floor of either House of Congress or in any cloakroom or lobby adjacent to that floor, in the Rayburn Room of the House of Representatives, or in the Marble Room of the Senate, unless authorized to do so pursuant to rules adopted, or an authorization given, by that House;
(B) enter or remain in the gallery of either House of Congress in violation of rules governing admission to the gallery adopted by that House or pursuant to an authorization given by that House;
(C) with the intent to disrupt the orderly conduct of official business, enter or remain in a room in any of the Capitol Buildings set aside or designated for the use of either House of Congress or a Member, committee, officer, or employee of Congress or either House of Congress;
(D) utter loud, threatening, or abusive language, or engage in disorderly or disruptive conduct, at any place in the Grounds or in any of the Capitol Buildings with the intent to impede, disrupt, or disturb the orderly conduct of a session of Congress or either House of Congress, or the orderly conduct in that building of a hearing before, or any deliberations of, a committee of Congress or either House of Congress;
(E) obstruct, or impede passage through or within, the Grounds or any of the Capitol Buildings;
(F) engage in an act of physical violence in the Grounds or any of the Capitol Buildings; or
(G) parade, demonstrate, or picket in any of the Capitol Buildings.

If Sheehan really did have a banner:

(f) Parades, Assemblages, and Display of Flags.— Except as provided in section 5106 of this title, a person may not—
(1) parade, stand, or move in processions or assemblages in the Grounds; or
(2) display in the Grounds a flag, banner, or device designed or adapted to bring into public notice a party, organization, or movement

Penalty for violation of the above is a fine under US Code Title 18 and/or up to 6 months in prison.