Article I, Section 5, Clause 2:
Each House may determine the Rules of its Proceedings, punish its Members for disorderly Behaviour, and, with the Concurrence of two thirds, expel a Member.
Congress has authority to make it an offense against the United States for a Member, during his continuance in office, to receive compensation for services before a government department in relation to proceedings in which the United States is interested. Such a statute does not interfere with the legitimate authority of the Senate or House over its own Members.1 In upholding the power of the Senate to investigate charges that some Senators had been speculating in sugar stocks during the consideration of a tariff bill, the Supreme Court asserted that
the right to expel extends to all cases where the offence is such as in the judgment of the Senate is inconsistent with the trust and duty of a Member.2 It cited with apparent approval the action of the Senate in expelling William Blount in 1797 for attempting to
seduce an American agent among the Indians from his duty and for negotiating for
services in behalf of the British Government among the Indians—conduct which was not a
statutable offense and which was not committed in his official character, nor during the session of Congress nor at the seat of government.3
In Powell v. McCormack,4 a suit challenging the exclusion of a Member-elect from the House of Representatives, it was argued that, because the vote to exclude was actually in excess of two-thirds of the Members, it should be treated simply as an expulsion. The Court rejected the argument, noting that House precedents were to the effect that the House had no power to expel for misconduct occurring prior to the Congress in which the expulsion is proposed, as was the case of Mr. Powell's alleged misconduct. The Court based its rejection on its inability to conclude that, if the Members of the House had been voting to expel, they would still have cast an affirmative vote in excess of two-thirds.5