While opinions differ sharply about President Trump, everyone can agree he speaks plainly. On Thursday he issued an executive order supporting free speech on campus. “Under the guise of ‘speech codes’ and ‘safe spaces’ and ‘trigger warnings,’ universities have tried to restrict free thought, impose total conformity, and shut down the voices of great young Americans,” he said at a White House ceremony. “If a college or university doesn’t allow you to speak, we will not give them money. It’s very simple.”

The president’s statement was bracing and lucid. Since we are talking about the federal government, however, execution of the order may not be as simple. Dozens of agencies dispense some $36 billion annually in federal grants to colleges and universities. Parsing exactly how violations will be identified and penalties assessed is a difficult question. Also, the order applies directly only to public institutions, which are required by law to uphold the First Amendment. Private schools are required only to abide by their own declared policies.

Some critics think the order is a prescription for havoc. “It’s essentially an order designed to create a lot of chaos and confusion,” said Jonathan Friedman, an administrator at PEN America, which describes itself as a free-speech advocacy group. Other critics went further, disputing whether free speech is actually in jeopardy on campus. An Inside Higher Ed report described the president’s remarks as “bombastic” and “unnecessary” because colleges and universities already “promote free speech and academic freedom as part of their mission.” Consequently, the executive order “is a solution in search of a problem.”

Against that contention is a veritable library of contrary evidence detailing a range of efforts to intimidate conservative students, enforce politically correct orthodoxy, and limit debate. Speakers from Ann Coulter and Ben Shapiro to George Will and Charles Murray have been attacked, pilloried, “deplatformed” or “disinvited” from colleges across the country. Hayden Williams, a 26-year-old recruiter for the conservative group Turning Point USA, was viciously attacked at the University of California, Berkeley last month. A headline at CNN said that he was “allegedly” attacked, but the accompanying video, which went viral, showed him being punched in the face.

With the president Thursday were several students who had been harassed or punished for expressing conservative views. One was Ellen Whitman, president of a pro-life group at Miami University of Ohio, who last fall asked the school for permission to set up a display of small wooden crosses representing lives lost to abortion. An administrator insisted that Ms. Whitman post signs around campus to warn other students about the “emotional trauma” that seeing the display might induce.

It is too early to say how much good the president’s executive order will do, but it was long past time for the federal government to face up to the rot of political correctness and intolerance that is subverting the American educational establishment. There are some points of light. The so-called Chicago Statement, for example, named for a declaration of principle from the University of Chicago, embraces open and robust debate even about subjects that “some or even by most members of the University community [find] offensive, unwise, immoral, or wrong-headed.” Several institutions have endorsed that document.

But many others, including some of the most prestigious, reject it outright. Students and professors at Williams College, confronted with an initiative to adopt the Chicago principles last year, took “grave issue” with its “premises” and warned of “the potential harm it may inflict upon our community.” You might have thought that supporting free speech was an obvious good. Not so fast. The Williams activists declared that the notion “has been co-opted by right-wing and liberal parties as a discursive cover for racism, xenophobia, sexism, anti-semitism, homophobia, transphobia, ableism, and classism.”

The authors of the Williams counterpetition made a show of demanding greater diversity at the 226-year-old Western Massachusetts school. But it’s long been obvious that calls for “diversity” usually amount to demands for strict intellectual and moral conformity on contentious issues. By that inverted standard, a campus is more “diverse” the fewer voices it tolerates.

This is precisely the situation that the president’s executive order promoting free speech on campus is designed to address. That its effect is likely to be more hortatory than coercive may be an advantage, not a liability, since serious reform of these institutions will come about not from the imposition of a law but a change of heart. The prospect of losing federal dollars is one sort of incentive. The spectacle of those passionate, articulate and besieged young students may prove to be an even greater one.