President Trump has frequently accused social media companies of violating constitutional free-speech protections. When he blocked Twitter followers for criticizing him, he ran afoul of the same standard, a federal appeals court says.

While the president set up his @realdonaldtrump account, which has more than 60 million followers, more than eight years before he gained public office, he blurred the lines by billing it as belonging to the 45th president and using it to make policy statements, the 2nd Circuit Court of Appeals found in a ruling on Tuesday. Those include announcing the dismissal of former White House cheif of staff Reince Priebus and discussing North Korea's development of nuclear weapons.

"Once the president has chosen a platform and opened up its interactive space to millions of users and participants, he may not selectively exclude those whose views he disagrees with," the court said, upholding a Manhattan federal judge's decision in a complaint filed by the Knight First Amendment Center at Columbia University.

Since Trump uses his account in a public capacity, blocking followers — which inhibits their ability to respond to and comment on the president's tweets — would violate their First Amendment rights, the judges ruled.

The decision, which follows a similar ruling involving a local government official from the 4th Circuit Court of Appeals in Richmond, comes amid increasing use of social media by governments. By applying longstanding case law to digital platforms, the decisions make clear that constitutional protections carry over into the digital realm, the plaintiffs say.

In Trump's case, his personal Twitter account "has become for better and for worse, maybe, the most important communications channel for this particular administration," said Jameel Jaffer, director of the Knight First Amendment Center. The lower court's ruling in the Knight Center's favor has already been cited in a number of other cases, he noted.

A three-judge panel on the appeals court brushed aside Trump's argument that despite the account's high public profile, he was acting as a private citizen when he blocked seven users.

That position "founders in the face of the uncontested evidence in the record of substantial and pervasive government involvement with, and control over, the account," the court ruled.

Trump himself has described use of the @realdonaldtrump account as "modern day presidential," the court noted, and White House social media director Dan Scavino has called it a channel through which Trump "communicates directly with you, the American people," the ruling noted.

"Because the president, as we have seen, acts in an official capacity when he tweets, we conclude that he acts in the same capacity when he blocks those who disagree with him," the judges said. “The fact that any Twitter user can block another account does not mean that the President somehow becomes a private person when he does so,” the judges wrote.

The decision may sharpen Trump's complaints about Twitter, where he posts prolifically but has also aired his grievances in a private Oval Office meeting with CEO Jack Dorsey.

Last month, the president complained in a telephone interview with Fox Business anchor Maria Bartiromo that his Twitter following would be much larger but for the company's hindrance.

"I have millions and millions of followers, but I will tell you they make it very hard for people to join me on Twitter; they make it very much harder for me to get out the message," said Trump, whose following is the 12th-highest worldwide. "If I announced tomorrow that I was going to become a nice liberal Democrat, I would pick up five times more followers."

Twitter has repeatedly denied such accusations, noting that workers attempt to keep the platform healthy by removing fake accounts employed to manipulate or harass users. That sometimes leads to smaller follower counts for prominent posters, the company has said, but boosts user confidence.

Trump and his allies in Congress say Twitter and its social media rivals, based in Silicon Valley, employ liberal workers who conspire to suppress conservative views, a point GOP lawmakers have made in a series of congressional hearings. Democrats have countered that the Constitution prohibits government regulation of free speech but doesn't apply the same standard to individuals or businesses.