Last week, the University of Chicago (UChicago) sent a letter to incoming students affirming the university’s commitment to robust and even uncomfortable dialogue and debate on campus.

While many—including FIRE—lauded the university’s statement, some critics argued that the letter’s statement that it does not support “so-called ‘trigger warnings’” was unnecessary since no universities actually mandate trigger warnings. For example, the New Republic’s Jeet Heer accused UChicago of “attacking academic freedom,” quoting a tweet from City University of New York professor Angus Johnston:

A professor’s use of trigger warnings isn’t a threat to academic freedom. It’s a MANIFESTATION of academic freedom. — Angus Johnston (@studentactivism) August 25, 2016

FIRE has uncovered evidence to the contrary. In fact, there are several colleges and universities that, as part of their sexual misconduct policies and procedures, require professors to use trigger warnings in the classroom.

While I was updating Drexel University’s entry in FIRE’s Spotlight Database, I noticed that the university’s Sexual and Gender-Based Harassment and Misconduct Policy states that “[i]t is expected that instructors will offer appropriate warning and accommodation regarding the introduction of explicit and triggering materials used.”

And a quick Google search reveals that Drexel is not alone in instituting this requirement. Identical language can be found in sexual misconduct policies at Bay Path University, Colby-Sawyer College, North Iowa Area Community College, and St. Vincent’s College. And these are just the schools that phrase their requirement in the same terms; there may be others out there, as well.

So there are, indeed, a number of schools that require faculty to use trigger warnings under certain circumstances. And in FIRE’s experience, once the genie is out of the bottle, it’s difficult to put back in.

Just look, for example, at the proliferation of bias incident reporting systems across the country over the past few years. FIRE has been sounding the alarm about those policies since 2007, but only recently have others—including the New Republic—begun to take note of the threat they pose to free speech on campus.

I suspect we will see more trigger warning requirements in the months and years to come, making the University of Chicago’s stand to the contrary all the more significant.