President Donald Trump has been sued by a group of critical Twitter users blocked from following him on the social network.

The lawsuit (PDF), filed Monday in federal court in Manhattan, argues the practice violates the First Amendment of the US Constitution. The seven Twitter users say Trump blocked them from following him on Twitter for criticizing or mocking him on the social network.

Lawyers for the Knight First Amendment Institute at Columbia University, who are part of the lawsuit, argue that the president's blocking of users "imposes an unconstitutional restriction on their participation in a designated public forum."

The request raises First Amendment issues related to the president's use of Twitter to make prolific and often controversial statements about public policy. The blockages suppress free speech by limiting users' ability to view his tweets and comment on them, the group said in a previous letter seeking to be reinstated as followers of Trump on Twitter.

"Everyone being able to see the president's tweets feels vital to democracy," Joseph Papp, one of the seven Twitter users involved in the suit, said in a statement.

Papp said he had been a registered Republican for 10 years and didn't join the suit for political reasons, but that he "felt a deep sense of unease" when he was blocked.

The White House didn't immediately respond to a request for comment.

The lawsuit, which seeks an injunction to require the president to unblock users, also names White House spokesman Sean Spicer and Dan Scavino, the White House director of social media, as defendants.

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