Naomi Reice Buchwald of the U.S. District Court in the Southern District of NY ruled that Twitter serves as a "designated public forum" and is protected under the plaintiffs' First Amendment, which is the aspect of U.S. Constitution that deals with free speech.
"The blocking of the individual plaintiffs from the @realDonaldTrump account due to their expressed political views violates the First Amendment", declared the judge, a Clinton appointee who serves on a court in NY.
The judge ordered Trump to unblock his account.
"We're pleased with the court's decision, which reflects a careful application of core First Amendment principles to government censorship on a new communications platform", said executive director of the Knight Institute, Jameel Jaffer, in a press release.
After a hearing this year, the judge had suggested that Trump mute rather than block some of his critics.
Katie Fallow, a staff attorney at Knight who represented the plaintiffs, said the ruling "should guide all of the public officials who are communicating with their constituents through social media".
"We certainly hope that other public officials will take note of the ruling and will operate their social media accounts consistent with the First Amendment restrictions on their ability to silence critics", DeCell said.
Columbia University's first amendment organization, the Knight Institute, made a decision to take up O'Reilly's case, arguing that Trump was violating her First Amendment rights by doing so-even if it's from his personal account.More news: Voices raised for Manchester bomb dead
In other words, because Trump and his social media team are not in a position to control subsequent discussion of any tweets in the comment threads, then by blocking citizens from being a part of that public discussion they are limited their free speech rights.
Trump has more than 50 million followers.
"In sum, we conclude that the blocking of the individual plaintiffs as a result of the political views they have expressed is impermissible under the First Amendment", Buchwald wrote in the 75-page ruling.
When it comes to Twitter, the First Amendment grants the American people the right to speak about the President - but it doesn't force him to listen.
The case raised First Amendment issues related to the president's use of Twitter to make prolific and often controversial statements about public policy.
The Justice Department and Twitter are yet to comment on the ruling.
New York Southern District Judge Naomi Reice Buchwald decided that this was indeed the case. But if Trump muted an account, he would not see that user's tweets but the user could still see and respond to his. "The court says this is a designated public forum and the general presumption is everyone can enter".
The case came after a number of individuals brought a case against Trump after he blocked them for posting critical messages about him. Like so many bullies, Trump has exceedingly thin skin and has a habit of blocking people who mock or disagree with him.