The Volokh Conspiracy
Mostly law professors | Sometimes contrarian | Often libertarian | Always independent
Rep. Marjorie Taylor Greene was stripped of committee assignments because of her pre-election-campaign statements embracing QAnon, 9/11 trutherism, claims that school shootings were faked, Rothschild space lasers, and executing Democrats. (She has apparently renounced most or all of the claims since.) Does that violate the First Amendment?
I think the answer is "no": Committee appointments are a political process, and are subject to political decisions, including ones based on a person's constitutionally protected speech. Just as the President is entitled to nominate cabinet members and judges based on past speech he likes—and reject possible nominees based on past speech he dislikes—so Congress can dole out committee positions the same way.
We see this in the longstanding practice of giving members of the majority party more seats on committees. Applied to low-level government employees, such partisan hiring decisions would violate the First Amendment. But when it comes to high-level executive decisionmakers, they are generally just fine, and likewise for Congress. You have a First Amendment right to belong to the minority party, but that means you're less likely to get the committee assignment you want (since your party has fewer seats on the committees).
Likewise, my sense is that party loyalists are more likely to get the best spots. Again, opposing the party leadership is constitutionally protected against criminal punishment or civil liability, but not against political decisions such as appointment to one or another committee (and, again, same with high-level Executive Branch appointments or judicial appointments). And it's true as to other speech protected by the First Amendment, recent or past.
There might be First Amendment limits as to other forms of discipline or expulsion (see dictum in Boehner v. McDermott (D.C. Cir. 2007)), whether or not courts could enforce those limits. But that's a separate matter, I think, from choice of Congressional leadership positions, or from committee assignments.
This having been said, such decisions might be a bad idea. In the words of Jonathan Rauch,
For all its New Testament rhetoric, Washington is an Old Testament city. It is a city which holds, with Beowulf, that it is better to avenge a friend than mourn him. The only rule of conduct is, "Do not unto me, for I will in return do worse unto you."
It might be better for the majority party to leave a freshman minority party Representative with her typical modest freshman assignments, rather than to invite an escalating tit-for-tat the next time party control flips. (Voters on both sides sometimes elect members who say some pretty offensive things.) But I can't speak to that; all I can say is that the Constitution doesn't prevent committee assignments from being a political process, based in part on members' political activity and political speech.