Trump's blocking of Twitter critics unconstitutional - US appeals court

US president Donald Trump violated the constitution by blocking people whose views he disliked from his Twitter account, a federal appeals court ruled on Tuesday.

In a 3-0 decision, the 2nd US Circuit Court of Appeals in Manhattan said the First Amendment forbids Trump from using Twitter's blocking function to limit access to his account, which has 61.8m followers.

"The First Amendment does not permit a public official who utilises a social media account for all manner of official purposes to exclude persons from an otherwise-open online dialogue because they expressed views with which the official disagrees," wrote circuit judge Barrington Parker, citing several supreme court decisions.

Kelly Laco, a spokeswoman for the US department of justice, which argued the appeal, said: "We are disappointed with the court's decision and are exploring possible next steps."

The White House declined to comment. White House social media director Dan Scavino was also a defendant. Twitter declined to comment as well.

Trump has made his @RealDonaldTrump account, which he opened in 2009, a central and controversial part of his presidency, using it to promote his agenda and to attack critics.

His blocking of critics was challenged by the Knight First Amendment Institute at Columbia University, as well as seven Twitter users he had blocked.

"The decision will help ensure the integrity and vitality of digital spaces that are increasingly important to our democracy," said Jameel Jaffer, Knight's executive director.

Tuesday's decision upheld a May 2018 ruling by US district judge Naomi Reice Buchwald in Manhattan, which prompted Trump to unblock some accounts.

The justice department had called her ruling "fundamentally misconceived," saying Trump used Twitter to express his views, not to offer a public forum for discussion.

Parker, however, said Trump's account bears "all the trappings of an official, state-run account" and is "one of the White House's main vehicles for conducting official business".

He said Trump and his aides have characterised the president's tweets as official statements, and that even the National Archives considers them official records.

Parker also found it ironic that Trump censored speech at a time the conduct of the US government and its officials is subject to intense, passionate and wide-open debate.

"This debate, as uncomfortable and as unpleasant as it frequently may be, is nonetheless a good thing," he wrote. "We remind the litigants and the public that if the First Amendment means anything, it means that the best response to disfavoured speech on matters of public concern is more speech, not less."