Twitter is suing the US government after it demanded it reveals the identity of an anti-Trump account.

The @ALT_USCIS profile was an anonymous profile account criticising President Trump’s immigration policy.

The account claimed it was being run by federal employees at the United States Citizenship and Immigration Services.

Twitter has requested a court block the Trump administration’s request, calling it a matter of free speech.

The challenge was filed in San Francisco, where the micro-blogging service is based.

"The rights of free speech afforded Twitter's users and Twitter itself under the First Amendment of the US Constitution include a right to disseminate such anonymous or pseudonymous political speech,” the company argued.

It added that the government "may not compel Twitter to disclose information regarding the real identities of these users without first demonstrating that some criminal or civil offense has been committed".

The move was backed by the American Civil Liberties Union.

"We are pleased to see Twitter standing up for its users' rights, and the ACLU will soon be filing documents in court on behalf of this user," the ACLU said in an emailed statement.

"To unmask an anonymous speaker online, the government must have a strong justification. But in this case the government has given no reason at all, leading to concerns that it is simply trying to stifle dissent."

Import law

In January, when Donald Trump became President Trump, several so-called "alternative" accounts for US government services began appearing online.

Most claimed to be authored by current or former employees at those agencies, and they offered harsh criticisms of their new boss.

According to the filing, the government sought to use a power given to the US Customs and Border Protection (CBP) - one typically used to obtain records relating to imported merchandise - to get detailed information on who was behind @ALT_USCIS.

The request asked for "all records regarding the twitter account @ALT_USCIS to conclude, User names, account login, phone numbers, mailing addresses, and I.P addresses".

It demanded Twitter hand over the information by 13 March 2017 - though the company was not actually sent the request until the 14th.

The account's profile image

In response, Twitter has told the court that "permitting the CBP to pierce the pseudonym of the @ALT _UCCIS account would have a grave chilling effect on the speech of that account in particular and on the many other 'alternative agency' accounts that have been created to voice dissent to government policies".

The account itself tweeted on Thursday the portion of the US Constitution that protects free speech.

Alternative accounts

The accounts were motivated by the gagging of the official National Parks Service Twitter account which, on the day of President Trump's inauguration, retweeted a picture comparing his crowd size to that of President Obama's inauguration in 2009. It was briefly shut down, before reappearing with an apology for the tweet.

According to press reports at the time, President Trump himself called the head of the National Parks Service to complain.

The furore prompted an apparent "rogue" former employee at the Badlands National Park in South Dakota to commandeer the park's Twitter account to published a variety of statistics and facts relating to climate change.

The tweets were quickly removed and the former worker's access revoked - but not before a flurry of new accounts claiming to be from within agencies appeared.

The veracity of the accounts was hard to verify given the authors insisted on keeping their identities secret in order to protect their jobs.