Can Congress' rules be unconstitutional?

Question

I'm very interested in U.S. Constitutional law and do a lot of mock government. One of the questions that I have been considering is whether it is possible for a rule Congress sets for its proceedings to be unconstitutional. For example, I was recently considering the constitutionality of Senate Rule XIX, which reads

No senator in debate shall, directly or indirectly, by any form of words impute to another Senator or to other Senators any conduct or motive unworthy or unbecoming a Senator.

This, to me, seemed like it could violate a Senator's First Amendment rights. Having previously asked this question here, however, my understanding is that, by consequence of the Rulemaking Clause and the Speech and Debate Clause, the Courts cannot consider a question of the constitutionality of a house's rules and the question of whether a restriction imposed by those rules on any particular speech by any particular member is constitutional. And, in fact, that the only body that has the power to decide whether a Senate rule is inconsistent with the constitution is the Senate.

I am still unsatisfied with this answer, however. I was considering some extreme cases: What if the Senate whipped members to maintain order and decorum? What if a Senate rule enforced racial segregation? These are clearly illegal and unconstitutional. Can the Courts still not review such rules? If they can, how are those cases different from Rule XIX? I am rather confused and would appreciate help in understanding this. Thank you!

Answer 1

United States v. Ballin, 144 U.S. 1 (1892) asked whether a congressional rule relating to determining quorum comported with constitutional requirements. In deciding that the rule was valid, the Court said:

Neither do the advantages or disadvantages, the wisdom or folly, of such a rule present any matters for judicial consideration. With the courts the question is only one of power. The Constitution empowers each house to determine its rules of proceedings. It may not by its rules ignore constitutional restraints or violate fundamental rights, and there should be a reasonable relation between the mode or method of proceedings established by the rule and the result which is sought to be obtained. But within these limitations all matters of method are open to the determination of the house...

That path to review is narrow (Rangel v. Boehner, 20 F.Supp.3d 148 (D.D.C. 2013)): "judicial intervention in this context is only 'appropriate where rights of persons other than members of Congress are jeopardized...'. judicial review of House Rules can take place only within a limited set of circumstances and may concern only a similarly limited set of constraints on the Rules. Here, Rangel does not challenge a particular House or Committee Rule as violative of the Constitution or of his fundamental rights."