A group of Twitter users blocked by President Donald Trump are suing after a request to be unblocked on First Amendment grounds went unheeded.

Knight First Amendment Institute at Columbia University v. Trump, filed in the Southern District of New York by the Knight First Amendment Institute at Columbia University on behalf of seven Twitter users, alleges Trump blocked them after they posted statements critical of the president on the social media platform.

In the complaint filed Tuesday, plaintiffs claim the move violates the First Amendment. The president's account, they allege, represents a public forum and is open to participation by the public. Blocking individuals who are critical of the president and his policies represents an unconstitutional viewpoint-based restriction, they said.