Twitter-happy Trump blocking people 'unconstitutional', rules US judge

US President Donald Trump cannot legally block his followers on Twitter based on their political views, a federal judge ruled today.

Twitter-happy Trump takes to the micro-blogging site to announce major policy decisions of his administration, promote his agenda and attack political rivals.

Trump, with more than 52 million followers, is the most followed world leader on the micro-blogging site.

US District Judge in New York Southern District Naomi Reice Buchwald gave her ruling on a petition filed by a group of seven followers who alleged that president Trump unlawfully barred them from viewing his feed.

As such the court was asked to consider whether a public official may, consistent with the First Amendment, "block" a person from his Twitter account in response to the political views that person has expressed, and whether the analysis differs because that public official is the US President.

"The answer to both questions is no," Buchwald said in her 75-page judgement.

"The viewpoint-based exclusion of the individual plaintiffs from that designated public forum is proscribed by the First Amendment and cannot be justified by the President's personal First Amendment interests," the judge said.

The ruling was welcomed by the petitioners.

"We're pleased with the court's decision, which reflects a careful application of core First Amendment principles to government censorship on a new communications platform," said Jameel Jaffer, executive director of Knight First Amendment Institute at Columbia University, which had filed the lawsuit on behalf of the group.

"The President's practice of blocking critics on Twitter is pernicious and unconstitutional, and we hope this ruling will bring it to an end," he said.

The US Department of Justice, however, disagreed with the court ruling.

"We respectfully disagree with the court's decision and are considering our next steps," Kerri Kupec, Justice Department spokesperson said.

"We hold that the speech in which they seek to engage is protected by the First Amendment and that the President and Scavino exert governmental control over certain aspects of the @realDonaldTrump account, including the interactive space of the tweets sent from the account," the judge said.

That interactive space is susceptible to analysis under the Supreme Court's forum doctrines and is properly characterised as a designated public forum, judge Buchwald said.

Twitter is a social media platform with more than 300 million active users worldwide, including some 70 million in the United States.