2 U.S.C. § 1613

(a) Prohibition Any person described in subsection (b) may not make a gift or provide travel to a covered legislative branch official if the person has knowledge that the gift or travel may not be accepted by that covered legislative branch official under the Rules of the House of Representatives or the Standing Rules of the Senate (as the case may be). (b) Persons subject to prohibition The persons subject to the prohibition under subsection (a) are any lobbyist that is registered or is required to register under section 1603(a)(1) of this title , any organization that employs 1 or more lobbyists and is registered or is required to register under section 1603(a)(2) of this title , and any employee listed or required to be listed as a lobbyist by a registrant under section 1603(b)(6) or 1604(b)(2)(C) of this title.