Trump has been blocking tweets that criticize him.
It took more than 280 characters, but a federal judge in Manhattan ruled Wednesday that President Trump and his aides can not block critics from seeing his Twitter account simply because they had posted caustic replies to his tweets in the past.
"The answer to both questions is no", Buchwald wrote at the top of her opinion.
Jameel Jaffer, the Knight Institute's executive director, said the ruling broke some new ground for how the First Amendment is applied to digital space.
The judge declared that "because no government official is above the law and because all government officials are presumed to follow the law once the judiciary has said what the law is, we must assume that the president and [digital director Dan] Scavino will remedy the blocking we have held to be unconstitutional".
In the past week, he has repeatedly claimed in multiple tweets that the Justice Department put a "spy" inside his presidential campaign to frame him for "crimes he didn't commit" amid mounting questions over his campaign's possible collusion with Russian Federation.
Under the ruling, Buchwald did not order Trump to unblock his followers, saying that a finding that clarifies the law is sufficient to resolve the dispute.
In ruling, she said no government official - including the president - is above the law.
Trump has more than 50 million followers.
"The judge is taking a social media account launched well before Donald Trump was a public official and declaring it to be a public forum".
"The US District Judge also said that the viewpoint-based isolation of the individual plaintiffs from that assigned public hearing is ordered by the First Amendment and can not be supported by the President's personal First Amendment interests".
The decision is a remarkable coda to one of the more peculiar debates of Trump's presidency, and a victory for the First Amendment advocates who brought the lawsuit previous year.
U.S. district judge Naomi Reice Buchwald ruled on Wednesday that Trump, who has blocked several Twitter users who have been critical of him in the past, is violating the U.S. Constituion.
"The President, like other public officials, routinely engages in conduct that is not state action, whether that might be giving a toast at a wedding or giving a speech at a fundraiser", the Justice Department wrote in a brief, according to The Washington Post.
"I think this decision is correct", Giampietro said.
A spokesman for the US Department of Justice, which represents the president in the case, had no immediate comment.
Twitter has always been dogged by questions about how far its users' right to speech may extend.
It was argued that as an elected official Trump's Twitter is a valid channel for official communication - a White House press office probably just choked on its skimmed latte - and should be openly accessible to anyone.