With the US George Santos controversy in mind the 2018 Congressional Research Service Expulsion of Members of Congress: Legal Authority and Historical Practice report states
The U.S. Constitution expressly grants each house of Congress the power to discipline its own Members for misconduct, including through expulsion, stating that: [e]ach House may determine the Rules of its Proceedings, punish its Members for disorderly Behaviour, and, with the Concurrence of two thirds, expel a Member.
Expulsion is the process by which a house of Congress may remove one of its Members after the Member has been duly elected and seated. The Supreme Court has considered expulsion to be distinct from exclusion, the process by which the House and Senate refuse to seat Members-elect. In so concluding, the Supreme Court has held that exclusion cannot be used as a disciplinary tool, and Congress, accordingly, cannot undertake disciplinary measures on Members until after those Members have taken the oath of office.
The constitutional limits on the power of expulsion are informed by the Expulsion Clause’s text, historical background, judicial precedent, and historical practice. Presently, the only explicit standards for expulsion are the requirement for approval of two-thirds majority of the body imposing the punishment and the requirement that the individual subject to the expulsion has been formally seated as a Member of that body. The history of the Expulsion Clause suggests that the expulsion power is broad and confers to each house of Congress significant discretion as to the proper grounds for which a Member may be expelled. Accordingly, courts generally have declined to adjudicate the standards by which expulsions might be considered in the House or Senate. To date, 20 Members of Congress have been expelled: 5 in the House and 15 in the Senate. A large majority of those expulsions were predicated on Members’ behavior deemed to be disloyal to the United States at the outset of the Civil War. Nonetheless, the two most recent expulsions followed Members’ convictions on public corruption charges. One significant area of debate is whether a Member can be expelled for behavior arising prior to his or her election. The historical practice in each house of Congress is limited and mixed as to whether such expulsions are appropriate. The extent to which these historical practices could be said to bind Congress as precedent is unclear, as is Congress’s authority to discipline Members for conduct that occurred prior to their election or reelection to office. These debates are centered on two general concerns that may be in tension with each other: maintaining the ability of each house of Congress to preserve the integrity of the institution and overriding the will and right of constitutents to choose their representatives.
This report discusses the nature of the power of Congress to remove a Member, including the historical background of the Clause, the implications of the limited judicial interpretations of the Clause’s meaning, and other potential constitutional limitations in the exercise of the expulsion power. The report then analyzes the potential grounds upon which a Member might be expelled, including an overview of past cases resulting in expulsion and a discussion of the potential exercise of the expulsion power for conduct occurring prior to the Member’s election or reelection to Congress.
