Twenty-five years ago, in June 1992, the U.S. Supreme Court issued its opinion in the case of RAV vs. City of St. Paul. Two years earlier, a small cross made out of chair legs had been burned in the yard of the only African-American family living in the Dayton's Bluff section of St. Paul. Although other more serious criminal charges were available, the local prosecutor decided to charge those involved with a misdemeanor violation of a hate speech ordinance enacted by the City Council several years earlier but never used previously. The victimized family was not well-served by this decision.

The ordinance made it a crime not just to display a burning cross or a Nazi swastika, but to display any symbol (thus to express any opinion) that one knew or should have known would arouse "anger, alarm or resentment in others on the basis of race, color, creed, religion, or gender." This provision did not address the ordinary criminal conduct alleged but instead outlawed offensive speech based on the content of the speech and the viewpoint expressed.

As an appointed public defender, I, along with my co-counsel, Michael Cromett, challenged the constitutionality of this provision, arguing that the law violated the U.S. Constitution's First Amendment. The condensed history of what happened next is that:

(1) The District Court judge agreed with us and struck down the ordinance in June 1990.

(2) The Minnesota Supreme Court granted accelerated review, and a few months later unanimously reversed the district court, reinstating the ordinance.

(3) The U.S. Supreme Court granted review in June 1991, and a year later unanimously reversed the Minnesota Supreme Court in a landmark opinion authored by Justice Antonin Scalia.

So how did we convince the U.S. Supreme Court to grant review of a seemingly minor case involving a juvenile (RAV) and a city ordinance? And how did we convince the justices to then unanimously reverse the Minnesota Supreme Court?

Speech codes on college campuses.

We recognized early on that the St. Paul ordinance and speech codes both stemmed from the growing movement for what had then recently been labeled "political correctness." Our petition for a writ of certiorari analogized the St. Paul hate speech ordinance to the language of speech codes, just beginning to proliferate in spring 1991.

Long before "trigger warnings," "intellectual safe spaces" and "bias response teams," well-meaning but misguided administrators were aiding and abetting self-censorship at institutions of higher learning. The justices of the U.S. Supreme Court in 1991 reached out to take the case to address this growing threat to free speech. And address it they did.

Scalia, writing for the court, assiduously dissected the ordinance (and, indirectly, speech codes), concluding that the language resulted in content-based and viewpoint discrimination, stating that "the point of the First Amendment is that majority preferences must be expressed in some fashion other than silencing speech on the basis of its content. … Selectivity of this sort creates the possibility that the city is seeking to handicap the expression of certain ideas."

The court continued: "In fact the only interest distinctively served by the content limitation is that of displaying the city council's special hostility towards the particular biases thus singled out. That is precisely what the First Amendment forbids. The politicians of St. Paul are entitled to express that hostility — but not through the means of imposing unique limitations upon speakers who (however benightedly) disagree."

"Let there be no mistake about our belief that burning a cross in someone's front yard is reprehensible," Scalia concluded. "But St. Paul has sufficient means at its disposal to prevent such behavior without adding the First Amendment to the fire."

The reaction was immediate. The New York Times declared the decision "of landmark dimension, a declaration in favor of more speech rather than less." While some criticized the court for being racially insensitive, understandably given the cross-burning and the confusion over what is involved in a facial constitutional challenge, others understood the import for those who wanted to end the threat to free speech on campuses.

The New Republic exulted: "This is an occasion for the friends of free expression to dance in the streets … . In a stroke, [the court] has repelled the most serious threat to open debate that the current generation of students has experienced."

University speech codes in Wisconsin and California were soon struck down in federal courts. It appeared the growing threat of censorship on college campuses had been halted.

But now — now it appears we have to learn this hard lesson again.

At what point did the expectation arise that a student would be protected from an idea contrary to his or her own at an institution of higher learning? Or, as Sen. Bernie Sanders said recently of those who would prevent a conservative speaker from appearing on campus: "What are you afraid of — her ideas?"

We risk raising a generation of students in a false environment, shielding them from disturbing thoughts and contrary opinions, providing them with professors who are taught to engage in self-censorship, while serious debate on sensitive topics is avoided as too dangerous.

This erosion of the freedom to think what you want and say what you think, a freedom critically important to learning and debate, is insidious. Too often school administrators have allowed this climate of censorship to permeate the academic environment. The result is felt in the classroom, where students soon learn to remain silent or risk group opprobrium, and outside the classroom, where invitations to controversial speakers are withdrawn under pressure because the majority does not want to hear what the minority has to say.

It is the heckler's veto in all its bluster and shame.

While it is difficult to hear controversial, even intolerant, opinions that challenge one's strongly held beliefs, history has shown repeatedly that attempting to silence those who challenge those beliefs is a dangerous mistake. To react that way suggests those beliefs are not strong enough to survive a challenge.

An essential part of our American identity must always be an unwavering respect for, and devotion to, the right of free expression, even for those who disagree with us.

When I commenced my oral argument before the U.S. Supreme Court as appellant's counsel on Dec. 4, 1991, well aware that I was fortunate to have the opportunity to address the court, I began as follows:

"Each generation must reaffirm the guarantee of the First Amendment with the hard cases. The framers understood the dangers of orthodoxy and standardized thought and chose liberty."

The dangers of orthodoxy and standardized thought remain. It is time for this generation of students to choose liberty.

Edward J. Cleary is chief judge of the Minnesota Court of Appeals and author of "Beyond the Burning Cross." The opinions expressed here are solely his own.