This story was originally published on June 6, 2017. It has been updated to include new developments about the Knight First Amendment Institute's lawsuit.

President Trump's irate and irrational tweets have already gotten him in plenty of trouble, and will, no doubt, continue to be an issue as he pushes for approval of his controversial travel ban before the Supreme Court. Now, free speech advocates are suing Trump not just for what he's saying on the platform, but for what he's preventing his constituents from saying to him.

In a lawsuit filed today in the Southern District of New York, the Knight First Amendment Institute, an offshoot of the larger Knight Foundation that focuses on protecting First Amendment rights in the digital age, sued President Trump, press secretary Sean Spicer, and social media director Dan Scavino. The suit alleges that when Trump blocks people on Twitter, he's barring them from "an important public forum for speech." The list of plaintiffs includes several of those people.

The suit follows a letter sent to the President in June, which contended that the @realdonaldtrump Twitter feed is a "designated public forum," no different from a city council or school board meeting. The First Amendment bars the government from censoring individuals in such forums, based on their views. Through the letter, the Institute asked Trump to unblock these accounts and stop blocking people in the future. Trump (clearly) didn't comply and so, the Institute followed through with its suit.

"This is the bedrock principle," Katie Fallow, senior attorney at the Knight Institute, said at the time the letter was sent. "If there’s any kind of forum the government is operating for expression, it may not discriminate on the basis of viewpoint."

The lawsuit provides evidence indicating the President has done just that. One Twitter user, @AynRandPaulRyan, was blocked after tweeting a gif of the Pope looking grim with President Trump.

Another, @joepabike, found himself blocked after tweeting about the President's decision to pull out of the Paris Agreement last week.

By blocking certain people on Twitter, President Trump has made it impossible for them to speak directly to him. They can't see his Tweets. He can't see theirs. And they can't participate in the reply threads that are open to the general population. But the biggest issue, Fallow said, is that Trump is specifically blocking people based on how critical they are of him. Other people on Twitter may do that regularly, but when you're a government official, Fallow argued, different rules apply. "One of our major missions is to be committed to free speech in the digital age and make sure traditional First Amendment principles apply to new technology," she said.

But not all First Amendment scholars are convinced the Institute would have a strong case in court.

"The question of whether the President’s Twitter feed is a public forum is a more complicated question," says Neil Richards, a professor at Washington University's Law school, specializing in First Amendment theory. "The law here is famously muddled, because it’s trying to prevent the government from discriminating against people who speak on public streets and parks, but it’s trying to fight the urge to make everything a public forum."

If Twitter had been invented by the government explicitly as a portal of communication between the president and his constituents, the Institute might have a stronger argument, Richards says. But the @realdonaldtrump handle actually predates Trump's term in office. And while it is the account he uses most often, it isn't even his official @POTUS account, which was created by the White House.

Fallow acknowledged that the question of whether government social media accounts are public forums is a relatively new one. But she points to a case called Davison v. Loudoun County as evidence that the courts may have the Institute's back. In that case, a man named Brian Davison argued that Loudoun County, Virginia's board of supervisors violated his First Amendment rights by deleting a comment he left on the chair of the board’s Facebook page. Loudoun County moved to get the case dismissed, arguing that the Facebook page was her personal account, not her official government account. The court didn’t buy that argument and denied the county's move to dismiss.

Whether or not the Knight Institute's argument will win in court, Richards says, it's still a critical argument to make. "Freedom of speech is more than what the First Amendment protects," Richards says. For instance, creating a culture of truly free speech not only means protecting the press in court, but refraining from publicly disparaging the press on a daily basis, as the President is wont to do.

"Freedom of speech is not just what happens in lawsuits," Richards says. "What the Knight Institute is doing is a useful public service that starts an important conversation."

That conversation is sure to continue when the Supreme Court hears oral arguments in the case that will decide the long-term fate of President Trump's travel ban, which bars travelers from six predominantly Muslim countries from entering the US. The president has left a trail of digital bread crumbs about the ban dating back to his days on the campaign trail. When the ban's day before the Supreme Court comes, the question of how the law ought to treat Trump's tweets could become a central part of the court's debate.