Opinion | I Prosecuted the Capitol Rioters. I Know Why Trump Pardoned Them.

On Jan. 6, 2021, Jalise and Mark Middleton, a married couple from Texas, trespassed onto the Capitol grounds and joined thousands of rioters gathered at the building’s West Front.

The assembled mob was assaulting a thin line of officers, and pepper spray wafted through the air. Rather than retreating in the face of violence, the couple pushed up against the makeshift barrier the police had established, hit officers and tried to drag one into the crowd. They gave up only after they were pepper-sprayed themselves, and though they did not make it into the Capitol, they were proud of what they did: Afterward, Ms. Middleton wrote on Facebook, “We fought the cops to get in the Capitol and got pepper-sprayed and beat but by gosh the patriots got in!”

I know this because I was one of the scores of lawyers who prosecuted the rioters, and was part of the team that tried the Middletons specifically. (On Thursday, I left the Justice Department, and speak only for myself.) One moment from their trial has stuck with me. Sitting in the courtroom in the awkward minutes before their verdict was announced, I noticed that Mr. Middleton was wearing “TRUMP” socks, with the president’s face stitched into the side. That small sign of fealty struck me as incredibly sad. The Middletons were ready to go to prison for a man who, quite likely, didn’t care about them at all.

The Middletons were convicted on all counts, including charges of assaulting federal officers. But on Monday, Mr. Trump pardoned them and nearly 1,600 other people who attacked the Capitol in his name. I think he did so not out of sympathy for the rioters, but because their freedom serves his interests.

For while some convicted rioters seem genuinely remorseful, and others appear simply ready to put politics behind them, many others are emboldened by the termination of what they see as unjust prosecutions. Freed by the president, they have never been more dangerous.

Take Stewart Rhodes, whose Oath Keepers group staged firearms and ammunition near Washington on Jan. 6 in anticipation of a “bloody and desperate fight.” Or Enrique Tarrio, whose Proud Boys led rioters into the Capitol and who had declared just after the 2020 election that while he and his followers would not start a civil war, they would be sure to “finish one.”

They are now free to pursue revenge, and have already said they want it. Upon his release this week, Mr. Tarrio declared that “success is going to be retribution.” He added, “Now it’s our turn.”

The effect — and I believe purpose — of these pardons is to encourage vigilantes and militias loyal to the president, but unaccountable to the government. Illiberal democracies and outright dictatorships often rely on such militia groups, whose organization and seriousness can range widely, from the vigilantes who enforce Iran’s hijab dress code to the United Self-Defense Forces of Colombia that have killed government opponents.

Here in America, lynch mobs and the Ku Klux Klan bolstered a racial caste system with violence that state governments, for the most part, were unwilling to commit themselves. But for decades, we had little reason to fear that vigilantes or militias would enforce the will of the state.

That may be changing. Rioters who assaulted police officers at the Capitol have called for politicians who oppose Mr. Trump to be hanged, declared that “there will be blood,” and that “I plan on making other people die first, for their country, if it gets down to that.” But it’s not just their readiness for violence. One officer, who’d worked lots of riots, explained to me how Jan. 6 felt different: Most rioters know at some level what they’re doing is wrong, he said, but these guys thought they were right. Monday’s pardons will reinforce these rioters’ beliefs in their cause, and their loyalty to the man who leads it.

Mr. Trump seems excited about this possibility. When asked Tuesday if groups like the Proud Boys and Oath Keepers had a place in the political conversation, he said, “We’ll have to see,” adding that “these were people that actually love our country.”

There is great value to him in having members of these groups released, doubly loyal to him, and eager to carry out his agenda and silence his critics through violence. Mr. Trump has shown his willingness to use his pardon power, and little stops him from doing so again.

What might happen next? Vigilantes could harass, assault or even kill perceived enemies of the state. Under the thin pretext that these vigilantes were acting in self-defense, the president could pardon them for federal crimes, or pressure pliant governors to do the same for state ones. In such a scenario, the president could put those loyal to him above the law, quite literally. This kind of violence was a part of our past; it may be a part of our future.

This is a frightening possibility, but it is not an inevitable one. Groups like the Institute for Constitutional Advocacy and Protection at Georgetown Law are already working with state officials on legislation to shut down paramilitary activity that, among other things, interferes with government proceedings or people’s constitutional rights. Local law enforcement can and should prioritize protecting the groups that unlawful private militias may target first, such as immigrants, trans people and opposition politicians.

These efforts are particularly urgent now, because of how many of our elected officials have changed their calculus about the attack. Elise Stefanik, a Republican in the House, once said that the rioters should “be prosecuted to the fullest extent of the law.” Three years later, she was calling them “hostages,” and she is now the president’s pick for ambassador to the United Nations.

Shortly after the attack, Kelly Loeffler, then a Republican senator from Georgia, said that “the violence, the lawlessness and siege of the halls of Congress are abhorrent.” Yet in the years that followed, she repeatedly called the congressional investigation into the attack a “sham,” and said that any indictment based on its work “should be dismissed out of hand.” She, too, is now nominated to serve in the president’s cabinet. Even Mr. Trump once called Jan. 6 a “heinous attack,” and said “to those who broke the law, you will pay.” His position, quite obviously, has changed.

Though Congress is required by law to establish a plaque honoring police officers who defended the Capitol, congressional leaders have failed to do so. It seems astounding that they would deny recognition to those people who saved their lives. But some officials’ ambitions require doing exactly that.

The president’s pardons are part of this collective attempt at forgetting. Illiberalism depends on hiding the crimes of its past, whether it is Jair Bolsonaro, when he was president of Brazil, celebrating the 1964 military coup in his country, or Vladimir Putin’s government repudiating the acquittals of the Soviet Union’s political enemies.

The past matters a great deal to the enemies of democracy, and we should not cede it. Victims of Jan. 6 should sue Congress to have their memorial installed. And academics should save the hundreds of criminal complaints on the federal docket that explain in irrefutable detail what each defendant did that day.

The rest of us, too, must keep the horrors of Jan. 6 from being forgotten. Memorialize the day. Read about the attack, and watch the videos. Keep it alive in your conversations. Doing so matters. For in a time when many politicians’ careers depend on forgetting, memory itself is an act of resistance.