Critics of rising campus illiberalism have a new champion in Congress: Peter Roskam, the Illinois Republican who is chairman of the oversight subcommittee of the House Ways and Means Committee.

On Wednesday, Roskam stepped into the raging controversy over free speech on college campuses, warning in a subcommittee hearing that colleges are increasingly "shutting down the marketplace of ideas" by instituting free speech codes and requiring reporting of "micro-aggressions" — subtle or unintended slights toward minority groups that reinforce stereotypes.

Such free-speech infringements, Roskam said, could risk colleges' nonprofit status, making them a matter of concern for the tax-writing committee.

"I've heard from conservative students and faculty who were prohibited, shut down or even fired when trying to express their support for the sanctity of life, their concerns about immigration or Planned Parenthood or defense of Israel, or their view that the government needs to stick more closely to the guidance of the Constitution," Roskam said.

Rising political correctness at colleges has become a politically charged topic in recent years, with students increasingly demanding that controversial speakers be disinvited from campus or requiring that administrators institute policies that crack down on offensive speech.

Even President Obama has weighed in on the controversy over campus illiberalism, saying last year that limiting politically incorrect speech is a "recipe for dogmatism."

Yet Democrats were not convinced Wednesday that the debate was a matter for the oversight subcommittee or that political correctness relates to the tax code.

"I do not understand why we are here," said Rep. John Lewis, D-Ga. He noted that the subcommittee "does not have jurisdiction over future legislation, over freedom of speech, or college curriculum or school resources."

At particular issue, however, was the case of a Georgetown Law student who was told to stop political activism in favor of Sen. Bernie Sanders' presidential campaign because it could endanger the school's 501(c)3 status. Georgetown has since aimed to revise its policies relating to political activism.

And some of the witnesses played up the possible constitutional issues at hand. "Fifty percent of the colleges and universities that we look at have openly unconstitutional speech codes," testified Catherine Sevcenko, a lawyer for the Foundation for Individual Rights in Education, a group that promotes free speech at colleges.