Twitter has filed a lawsuit against the government following a request from the Department of Homeland Security for info about an anti-Trump administration account named @ALT_USCIS.

The Verge reports that Twitter’s lawsuit alleges that US Customs and Border Protection has attempted to use a “limited-purpose investigatory tool” to discover the identity of the person behind the Twitter account @Alt_USCIS, one of a number of “alt-gov” accounts believed to be run by former or current government employees critical of the Trump administration. The Twitter account describes itself as “immigration resistance.” Twitter’s lawsuit states that the account was used “to express public criticism of the Department and the current Administration.”

Twitter acknowledges in their lawsuit that the account claims to be a dissenting member of the US Citizenship and Immigration Services. Twitter received a summons from Customs on March 14th requesting digital records that could possibly reveal the identity of the account owner such as IP logs and account-linked phone numbers and email addresses.

The suit names The Department of Homeland Security alongside four other defendants: DHS secretary John Kelly, acting CBP commissioner Kevin McAleenan, and special agents Stephen P. Caruso and Adam Hoffman, who issued the information request order. The lawsuit that Twitter filed questions the authority to issue such a request. Twitter argues that the initial order from CPB cited a statute commonly related to taxes on the importation of merchandise into the US, which Twitter does not believe holds the sufficient authority to reveal a user’s information.

Twitter also stated that revealing the identity of the account user “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.” Twitter also believes that the account is protected under free speech, a claim that the ACLU has agreed with, pledging to support Twitter in the lawsuit.

We're glad Twitter is pushing back. We'll be going to court to defend this user's right to anonymous speech. https://t.co/tqj5XrNvgn — ACLU (@ACLU) April 6, 2017

Twitter has yet to comment on the lawsuit.