What are the grounds for expelling a member of Congress?

1. Constitutional basis and formal threshold

The explicit legal authority for expulsion is the Expulsion Clause in Article I, Section 5, Clause 2 of the Constitution, which vests each House with the power to discipline and, by a two‑thirds vote, expel a Member ^{[1] [4]}. The supermajority requirement was understood by the Framers as the primary guard against partisan misuse, rather than a specification of substantive limits on when expulsion may be applied ^{[2] [5]}.

2. No fixed list of offenses — broad but sparingly used

There are no enumerated statutory grounds in the Constitution that define precisely what conduct warrants expulsion, and judicial guidance has been limited; courts have generally treated expulsion as largely a congressional, self‑governing power ^{[3] [6]}. In practice, however, expulsions have been reserved for what Congress considers the "most serious violations" — historically disloyalty to the Union, criminal conduct tied to abuse of office (bribery, corruption), or actions that reflect serious discredit on the institution ^{[7] [8] [3]}.

3. Typical procedural path to expulsion

Expulsion proceedings usually begin with an ethics committee or special investigative body that examines allegations, collects evidence, holds hearings and makes recommendations to the full chamber; a resolution with explicit charges can initiate the process ^{[9] [10]}. If the committee recommends expulsion, the full House or Senate votes and may accept, reject or alter the recommendation, but final removal requires the two‑thirds concurrence of members present and voting ^{[1] [9]}.

4. Historical practice and precedents that shape judgment

Historically the Senate has expelled few members — 15 since 1789, 14 during the Civil War for support of the Confederacy — and the House likewise has used expulsion rarely, preferring censure or reprimand for lesser offenses; these precedents have constrained the institutional expectation that expulsion is exceptional ^{[4] [8] [7]}. Past cases cited by legal commentators and Congress itself show expulsions most often tied to treasonous conduct, disloyalty, or criminal acts intimately related to official duties ^{[7] [11]}.

5. Limits, judicial review, and political realities

Although courts have recognized the institutional logic behind the expulsion power, they have routinely declined to substitute judicial review for Congress’s self‑discipline in most cases, citing separation of powers and Speech and Debate protections; as a result, standards are shaped more by political judgment and precedent than by enforceable judicial doctrines ^{[6] [12]}. That latitude creates a dual reality: broad discretion on grounds for removal, but a practical reluctance to use expulsion absent compelling facts and political consensus, because the remedy is both irreversible and politically fraught ^{[2] [12]}.

6. Competing views and implicit agendas

Observers and scholars diverge on whether the lack of textual limits invites abuse or wisely preserves institutional self‑protection; supporters of broad discretion argue it lets each chamber defend its integrity, while critics warn the power can be wielded for factional advantage unless the supermajority constraint is respected — a tension reflected in congressional reports and historical commentary ^{[5] [12]}. Political actors may prefer resignation, criminal prosecution, or censure over expulsion when factions seek the optics of accountability without invoking the ultimate sanction ^{[10] [8]}.

Conclusion

Expulsion is constitutionally authorized, procedurally rooted in committee investigation and a supermajority vote, and substantively undefined in the text, which has produced a body of practice that reserves the sanction for severe misconduct — disloyalty, corruption, crimes tied to office, or conduct that gravely discredits the chamber — while leaving room for political judgment and controversy ^{[1] [9] [7]}.