Transgender service members represented by LGBTQ advocacy groups on Tuesday filed suit against the White House executive order that bans transgender people from serving in the military.

The order signed late Monday rescinded Biden administration policies that permitted transgender service members to serve openly according to their gender identity. The order said the “assertion” that one might identify as transgender would be a “falsehood … not consistent with the humility and selflessness required of a service member.”

Space Force Col. Bree Fram, a transgender woman who came out and transitioned while serving, told ABC News that banning transgender individuals from serving would bring a “collective harm to our national security.”

Transgender troops “are meeting or exceeding the high standards the military has set for performance, and they’re doing so here at home, around the world, and in every service, every specialty that the military has to offer,” Fram said, who was speaking in her personal capacity and not on behalf of the Pentagon.

According to the suit filed Tuesday by plaintiffs represented by GLBTQ Legal Advocates & Defenders Law and the National Center for Lesbian Rights, the order directs Secretary of Defense Pete Hegseth “to reverse the current accession and retention standards for military service and to adopt instead a policy that transgender status is incompatible with ‘high standards’” that the executive order lays out.

Sasha Buchert, a senior attorney at Lambda Legal who represented plaintiffs who sued and temporarily blocked a similar order in 2017 in the first Trump administration, called the new order “cruel” and said it “compromises the safety of our country.”

She told ABC News the order “will force transgender service members to look over their shoulder” and “stamp them with [a] badge of inferiority.”

Buchert said her firm and the Human Rights Campaign also intend to file suit.

“We have been here before…as we promised then, so do we now: we will sue,” Buchert said.

Buchert said transgender troops will now “worry about…whether they’re going to have to end their illustrious military careers by being drummed out of the military.”

“Trans military folks have been serving now for 10 years, openly and proudly and deploying to austere environments and meeting every service-based standard that their peers can meet,” said Buchert, who is a veteran.

The executive order, paired with another that demands the dissolution of diversity, equity, and inclusion “bureaucracy” in the Defense Department, came on Hegseth’s first day of work at the Pentagon.

A 2016 study conducted by RAND estimated 2,500 active service members were transgender — in addition to some 1,500 reservists.

RAND found in its study that the number of active-duty troops seeking transition-related care that “could disrupt their ability to deploy” ranged from as low as 29 to as high as 129.

The Department of Defense does not track transgender individuals as a separate population.

The executive order does not make reference to transgender individuals. It directs the Pentagon to update guidelines around medical standards for individuals diagnosed with gender dysphoria, a precursor to transition care that affirms one’s gender.

The Pentagon said in a statement to ABC News that it “will fully execute and implement all directives outlined” in all executive orders from the president.

Trump as a candidate said he would take aim at “transgender insanity” as president. The order says the military must root out “ideologies harmful to unit cohesion.”

The logic around cohesion is familiar, Buchert said.

“We’ve seen this as a country on many occasions. We’re still correcting improper discharges for people that were, you know, drummed out of the military based on discriminatory motives in the past,” she said.

Cassie Byard, a Navy veteran who served with a service member who was transgender, said she “never saw any adverse effect on readiness or cohesion.”

Fram believes openness about her identity has made her unit more cohesive.

“My being authentic is actually reflected back to me and builds the strong bonds of teamwork that we need at the military to succeed, because we need everyone to be able to bring their best self to work,” she said.

While the order brings a “period of uncertainty” as the Pentagon weighs updates to medical guidelines over a two-month window to implement it, Fram said “my job right now, and the job of every transgender service member, is simply to do our duty. It’s to lace up our boots and get to work and accomplish the mission that we’ve been given.”

“We swore an oath to uphold the duties that we’ve been given, [to] support the Constitution,” she added. “And we’re going to continue to do so, unless told otherwise.”

-ABC News’ Luis Martinez contributed to this report.