NEW YORK — Twitter defied a U.S. government request for records that could identify users behind an account opposed to President Donald Trump, and is challenging that order in court.

The company filed its lawsuit Thursday in a San Francisco federal court against the federal Department of Homeland Security and its Customs and Border Protection office, charging that their efforts to “unmask” the people behind the account violate the First Amendment.

Twitter said its users have a constitutional right to disseminate such “anonymous and pseudonymous political speech.” It declined to comment beyond the lawsuit. DHS likewise declined to comment.

The account in question is @ALT_uscis , a reference to the U.S. Citizenship and Immigration Services office. The account described its users to The Associated Press in February as employees and former employees of the agency.

In a Thursday interview, an American Civil Liberties Union lawyer now representing the account declined to discuss anything about the person or people currently involved in the account being targeted by the Trump administration. Documents supporting the Twitter accountholder’s right to speak anonymously online will be filed in the next few days, said Esha Bhandari, a staff attorney for the ACLU.