Charlottesville seems destined to become a symbol of the vexing challenges associated with freedom of speech in America. On Friday evening, a crowd seething with hatred and bigotry conducts a torchlight parade in a manner deliberately evocative of Nazi theater.

The next day they demonstrate, carrying semi-automatic weapons, clubs, shields, helmets, and pepper spray. There are numerous violent clashes between demonstrators and counter-demonstrators, culminating in a lethal ISIS-type assault by a neo-Nazi, who rams his car into a crowd, killing a young woman.

How should we untangle the First Amendment rights at stake in this nightmare scenario? Within the coiled events of Charlottesville lie two distinct issues: First, there is a constitutional rule prohibiting the state from engaging in viewpoint discrimination when determining who may speak in public spaces. Second, there is a constitutional rule authorizing the state to regulate speech that conveys a “true threat,” which is “a serious expression of an intent to commit an act of unlawful violence to a particular individual or group of individuals.”

The state cannot discriminate against unpopular views — even Nazi ideology

Last weekend’s Unite the Right rally attracted a motley group determined to proclaim racist and anti-Semitic views that were outrageous and indecent. Yet traditional First Amendment doctrine prevents the state from discriminating on the basis of viewpoint, even on the basis of opinions as despicable as those. It prohibited the city from disadvantaging the planned parade on the basis of its hurtful and offensive message. (Indeed, a federal judge so ruled on the morning of the torchlight march.)

Why does the First Amendment prevent official discrimination against such loathsome views? The question has become pressing for a new generation. A recent Pew Research Center poll found that 40 percent of millennials believe that government should be able to prevent people from communicating messages that are offensive to minority groups. In contrast, only 12 percent of those born from the mid-1920s to the mid-1940s would allow government to regulate speech in this way, only 24 percent of Baby Boomers would do so, and only 27 percent of those in Generation X. Can traditional First Amendment doctrine justify itself in contemporary circumstances, such as those we saw play out in Charlottesville?

At root, we protect freedom of expression — even hateful expression — in order to strengthen democratic legitimacy. We want everyone to be free to participate in the formation of public opinion, and we want the state to be responsive to public opinion. If these conditions are met, we may experience the state as responsive to us, to the individuals who make up this great democracy. This in turn gives us reason for civic loyalty and engagement, and perhaps even to acknowledge the state as representing us.

As the Supreme Court put it in 1931 in the seminal case of Stromberg v. California (which held that California could not ban the red flag of the Communist Party): “The maintenance of the opportunity for free political discussion to the end that government may be responsive to the will of the people and that changes may be obtained by lawful means ... is a fundamental principle of our constitutional system.”

Those who seek to ban totalitarian symbols may think they are preserving public law and order. But in Stromberg, the Court turned that argument on its head, observing that freedom of expression “was essential to the security of the Republic.” Stromberg understood that in a democracy persons can and do hold passionately divergent views; and the more diverse the society, the greater the disagreement.

When the state suppresses unpopular views, it gives those holding those views little reason to play by official rules. Why should they abide by laws whose enactment they could not influence through their speech and expression? Why should they trust officials whose election and decisions they were preventing from opposing? No republic is secure if its citizens lack respect for its government.

Paradoxically, therefore, the “verbal tumult, discord, and even offensive utterance” created by the expression of diverse views is, as the Court put it in another famous opinion, “not a sign of weakness but of strength.” The discord is a sign that all are participating in public discourse, that all care enough to seek to influence public opinion. But those whose views are excluded from public discourse are effectively excommunicated from our democratic polity, and in such circumstances the repressed tends to return with redoubled fury and ressentiment.

In Skokie, Illinois, the Nazis just wanted to march. In Charlottesville, they toted weapons.

Many of the Charlottesville marchers weren’t just shouting hateful slogans; they were carrying weapons. We must thus consider not merely the constitutional rule against viewpoint discrimination, but also the lack of constitutional protection for true threats.

Disagreement in the public agora is tolerable because it symbolically displaces actual physical conflict. To the extent that such communication verges on violence or the threat of violence, it loses the immunity of the First Amendment. No doubt the neo-Nazi who slammed his car into the Heather Heyer meant to express a distinct message of hate, but he will have no First Amendment defense when he is prosecuted for murder. Similarly, those who utter what traditional doctrine calls true threats cannot claim refuge in the First Amendment.

Jason Kessler, who applied for permit for the Unite the Right march, affirmed that he “absolutely intend[ed] to have a peaceful rally” and that his group would “avoid violence.” But these promises are inconsistent with the accessories worn by Kessler’s followers. There is only one social meaning conveyed by demonstrators who come armed with semiautomatic weapons, helmets, and clubs. If I were in the vicinity of thugs so armed, I would be afraid, and I think legitimately so.

In contrast to the notorious proposed 1977 Nazi march through Skokie, a city populated by Holocaust survivors, the Charlottesville marchers came dressed and armed for a fight. The damage those opposed to the the Skokie march feared was psychological. The constitutional conceptualization of such harm is complex. This is because, as John Stuart Mill pointed out a long time ago, ideas can often be hurtful and cause intense distress. I am genuinely upset when I encounter the views of long-dead anti-Semites. Analogous psychological shock is often inseparable from engagement with alien ideas that seem outrageous. For this reason, First Amendment doctrine has long rejected this kind of psychological harm as a justification for legal regulation.

In Charlottesville, marchers entered town intending physically to intimidate onlookers. As one commentator remarked, “These white supremacists showed up with their own militia. Can you even imagine what would have happened if black folks showed up to protests in Baton Rouge with a militia?” Why should we extend the mantle of First Amendment immunity to demonstrators who from the outset signify their intention physically to intimidate onlookers?

Of course, without an audience, the marchers would not have had anyone to intimidate. The president of the University of Virginia warned before the demonstration, “the organizers of the rally want confrontation; do not gratify their desire.” When I was a professor at the University of California Berkeley, I was once asked how the school ought to respond to a student-invited speaker, the Holocaust denier David Irving. My recommendation was to shun him. Irving ought to be given the opportunity to speak, I said, but the auditorium should be empty. Those who seek only to spread hateful lies and are not open to good faith public debate should not be accorded the respectful attention that we owe real partners in constructive dialogue.

But public parks are different from classrooms. The melee that engulfed Charlottesville could not have happened without the manifest provocations of the alt-right and of the counter-protesters, who were determined to contest the meaning of every inch of public space. That was their right, and I applaud their courage. Public space is a scarce resource, and there are often fierce struggles about the meanings that public parks and streets will be used to convey.

In an abstract and civil world, protesters and counter-protesters would each refrain from undermining each other’s communication. But such restraint is often not possible in the real and passionate world of actual politics. Charlottesville is exemplary. It witnessed continual skirmishes between the two groups, some of which were violent, to varying degrees.

In such circumstances, the primary responsibility of the police is to maintain public order, which is to say to keep the peace while each side communicates what they have mobilized to express. From eyewitness accounts, the police failed in this task throughout a day filled with incidents of violence and injury. We do not yet understand why the police were so passive for so long, but their absence vividly illustrates that without the maintenance of legal order, rights of freedom of speech mean little. The First Amendment protects expression, not riots. It protects the right to participate in the formation of public opinions, not the right to commit mayhem.

Charlottesville devolved into a riot, yet Americans — if not Trump — are drawing lessons from the speech they did hear

It is fair to say that in Charlottesville the two sides were locked in battle and not in conversation. There was no constructive dialogue between the demonstrators and counter-demonstrators. But this narrow frame is inadequate for assessing the constitutional significance of last weekend’s events. Considered from a broader perspective, each side made itself visible to, and heard by, a larger audience. Thanks to media coverage, the general public was empowered to absorb the deeper meaning of Charlottesville.

When the alt-right shouted “blood and soil” and “Heil Trump,” the public could discern the filth beneath their message. Charlottesville thus consolidated the judgment of public opinion, a judgment that remarkably encompassed a broad spectrum of heretofore polarized political perspectives. Even Sen. Orrin Hatch could tweet, “We should call evil by its name. My brother didn't give his life fighting Hitler for Nazi ideas to go unchallenged here at home.”

Charlottesville should thus be remembered not only as a tragedy, but also as the midwife of a popular verdict so powerful that it finally compelled Donald Trump to condemn, however grudgingly and momentarily, the Ku Klux Klan and neo-Nazis. In the civil rights era, the public opinion of the country turned against Southern segregationists when the violence of Bull Connor’s police became visible. The public opinion of the country analogously turned against the alt-right when it witnessed the turmoil of Charlottesville. The country was sickened not merely by the alt-right’s strutting and bullying, but also by its message of white supremacy.

As I write this, however, Trump has unexpectedly and unpredictably bridled against this compulsion, once again returning to the theme that the violence in Charlottesville was the fault of both sides. But so far, Trump’s bizarre volte-face seems to have sparked an even more intense backlash against the alt-right’s message of hatred. Charlottesville has pushed Trump’s racism out of the shadows, and the media have focused public attention on the grotesque moral deformities that have become suddenly and embarrassingly visible.

Charlottesville has thus fulfilled the fundamental purpose of the First Amendment: to pose for all of us the question of what we should do in light of what we now know.

Correction: This piece originally stated that American Nazis marched in Skokie, Illinois. They famously won the right to do so, but the organizers called off the march.

Robert C. Post is Sterling Professor of Law at Yale Law School. He served as dean of Yale law from 2009 to this year.

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