2 USC 1607 - Rules of construction

(a) Constitutional rights 
Nothing in this chapter shall be construed to prohibit or interfere with
(1) the right to petition the Government for the redress of grievances;
(2) the right to express a personal opinion; or
(3) the right of association,

protected by the first amendment to the Constitution.

(b) Prohibition of activities 
Nothing in this chapter shall be construed to prohibit, or to authorize any court to prohibit, lobbying activities or lobbying contacts by any person or entity, regardless of whether such person or entity is in compliance with the requirements of this chapter.
(c) Audit and investigations 
Nothing in this chapter shall be construed to grant general audit or investigative authority to the Secretary of the Senate or the Clerk of the House of Representatives.