A group of lawyers in the US has threatened legal action against Donald Trump for blocking users on his Twitter account, alleging that the action of the President violates the First Amendment of the US Constitution.

The lawyers from Columbia University's Knight First Amendment Institute wrote a letter to Trump on behalf of two Twitter users who have been blocked in recent weeks after mocking the President on the platform, Vox.com reported on 8 June.

They argued that Trump's Twitter account was a public forum, and banning users from viewing or engaging with his tweets based on their viewpoints suppresses free speech guaranteed by the First Amendment.

"The President must not be allowed to banish views from public discourse simply because he finds them objectionable," explained Jameel Jaffer, Executive Director, Knight First Amendment Institute.

The group points to a March ruling in which a federal court ruled that the First Amendment applied after the the Loudon county, Virginia, attorney's office created a Facebook page for discussing legal issues.

Once the page was opened up for public discussion, the court said, it could not arbitrarily exclude some citizens from participating in the conversation.

But experts are not in consensus on the outcome as this issue tests new legal waters with regard to the First Amendment's application to online forums.

Trump has an array of possible defences against this possible lawsuit centering on the argument that the Twitter account used to block users is used in his personal capacity, some legal experts have argued. 

"My sense is that the @RealDonaldTrump account though run by Trump on government time and from government property is the work of 'Trump-the-man', just as it was before (his election), and not Trump-the-president. His decisions about that account are therefore not constrained by the First Amendment," Eugene Volokh, Professor of Law at University of California, Los Angeles, School of Law was quoted as saying.

Another defence proposed by experts is that the Block feature on Twitter does not practically affect a user's ability to access Trump's Twitter feed because all they have to do is log off from their blocked account to access it.