A leading civil liberties group is vowing to challenge President Trump's sudden decision to ban transgender people from the U.S. military.
"I'd be shocked if they go ahead with including trans people who are already serving on the front lines honorably," said Joshua Block, of the American Civil Liberties Union’s LGBT Project. "If they try to do that, they'll have to go through us first."
President Obama's administration put in place policies last year allowing transgender service members to serve openly.
Block told Fox News the abrupt switch throws the process into chaos.
"The issue of trans people already serving in the military has already been resolved," he said. "Everyone supports that, not only the Senate but Trump's own Secretary of Defense and the Chairman of the Joint Chiefs."
The ACLU and other legal advocacy groups said that for now, they would take a wait-and-see approach before filing any lawsuits opposing the policy change.
"Once the Pentagon figures out what the president wants to do, and tries to put pen to paper," said Block, "we'll be ready to challenge whatever happens."
There had been a Pentagon delay in allowing new enlistments of transgender recruits, but it was unclear whom the broader policy would affect.
The ACLU's Lesbian Gay Bisexual Transgender & HIV Project has been involved in almost every legal fight over these kinds of discrimination claims.
That includes representing a Virginia high school student whose case went to the Supreme Court in recent months.
Gavin Grimm, 18, was born female but identifies as male. He was allowed to use the boys' restroom at his high school for several weeks in 2014. But after some parents complained, the school board adopted a policy requiring students to use either the restroom that corresponds with their biological gender or a private, single-stall restroom.
Grimm was backed by the Obama administration in his argument that the policy violates Title IX, a federal law that bars sex discrimination in schools. His case was put on hold in March after the Trump White House reversed and refused to support Grimm's case.