A university president said rules put in place this year to protect conservative viewpoints on Colorado campuses have harmed free speech and led to death threats against professors.
Republican lawmakers said conservative students are still being harassed.
The comments came as a handful of college officials and students went before the legislature's Joint Education Committee on Thursday to report on efforts to enforce the Academic Bill of Rights. All state-funded colleges adopted the policy this year under pressure from Republican lawmakers.
The measure encourages the schools to review student rights and campus grievance procedures "to ensure that intellectual and political diversity is explicitly recognized and protected and to ensure those rights are adequately publicized to students."
The colleges agreed to the policy after lawmakers killed a stronger measure that would have required them to let students file grievances against professors if they felt they were being harassed for their beliefs.
Professors at Metropolitan State College in Denver are concerned that some classroom topics may be off limits, interim President Ray Kieft told the committee. He cited discussions of stem cell research, a lightning-rod issue for some who say it amounts to abortion when embryos are killed.
Kieft said death threats against a Metro State political science professor have "sent a real chill across the campus." The professor, Oneida Meranto, said in March she was threatened after a student filed a complaint against her and told lawmakers he had asked to drop her class because she was biased against conservatives.
Meranto responded publicly that the student was failing, prompting the student to accuse her of violating his privacy rights. School officials said the threats against Meranto originated off campus, and the FBI has said it was investigating.
Sen. John Andrews (R), a committee member, said new complaints aired by students at the meeting demonstrate the need for stricter enforcement of the policy.
University of Colorado law student Mario Nicholas said a professor called him a Nazi after Nicholas complained when the professor told the class that "the 'R' in Republican stands for racist." The professor was chastised by the dean.
Metro State student William Pierce said he filed a grievance after a professor accused him of spying on the class for Republicans intent on enforcing the new policy.
Colorado State student Heather Schmidt said she complained because a professor criticized former president Ronald Reagan and drew a caricature of President Bush. She said when she complained, she was told to find another class. Sen. Ken Gordon (D) said he called that professor and was told he had been forced out of the classroom by death threats.
Rep. Lynn Hefley (R) said professors who violate the rules should be suspended.
Larry Penley, chancellor of the Colorado State University System, CU President Elizabeth Hoffman and University of Northern Colorado President Kay Norton told legislators they are enforcing the policy.