NEW YORK (Reuters) - A federal appeals court on Tuesday cast doubt on U.S. President Donald Trump’s ability to keep Twitter users whose political views he dislikes from responding to his own account, suggesting it might violate those users’ free speech rights.

Slideshow ( 2 images )

Trump has made his @RealDonaldTrump Twitter account an integral and controversial part of his presidency, using it to promote his agenda, announce policy and attack critics.

He had blocked many critics from his account, which prevents them from directly responding to his tweets.

U.S. District Judge Naomi Reice Buchwald ruled last May that this violated the users’ First Amendment rights, prompting Trump to unblock at least some of these accounts. The decision came in a lawsuit brought by the Knight First Amendment Institute at Columbia University and several Twitter users.

A lawyer for the U.S. Department of Justice, arguing for the president on Tuesday, urged three judges of the 2nd U.S. Court of Appeals in Manhattan to overturn Buchwald’s decision.

While Trump does use his Twitter account for government business, it was not a public forum, the attorney, Jennifer Utrecht, told the judges.

When Judge Barrington Parker asked why blocking users for their political views did not violate the First Amendment, Utrecht said blocking was akin to Trump walking away from a person trying to talk to him on the street.

The judges had fewer questions for Jameel Jaffer, the lawyer for the plaintiffs.

Jaffer said that although Twitter is a private platform, Trump was effectively inviting the public to participate in an open forum by using it for government purposes.

“The whole point of Twitter is to facilitate interactions between users,” Jaffer said.

The individual plaintiffs in the lawsuit include Philip Cohen, a sociology professor at the University of Maryland; Holly Figueroa, described in the complaint as a political organizer and songwriter in Washington state, and Brandon Neely, a Texas police officer.

It is not known when the court will issue a ruling on the case.