The decision reversed a policy initially approved by the Defense Department under former President Barack Obama, which was still under final review that would allow transgender individuals to openly serve in the military.
Lambda Legal and OutServe-SLDN immediately filed suit last week on behalf of three individuals, one of whom is now serving in the military and two who seek to join, and two human rights organizations.
The lawsuit also argues the ban discriminates based on sex and transgender status. "Men and women who are transgender with the courage and capacity to serve deserve more from their commander-in-chief".
The ACLU has filed a separate suit in the United Stated District Court for the District of Maryland by the ACLU on behalf of transgender service members, including Petty Officer First Class Brock Stone and others.
Trump ordered the military to stop paying for transition-related medical expenses, unless the service members' health was in jeopardy, and the ACLU asked the judge to reverse that order immediately.
Staff Sergeant Cole has served in the U.S. Army for nearly 10 years, including a one-year deployment to Afghanistan where she served as a team leader and designated marksman.
In a press release about the OutServe-SLDN lawsuit, Lambda Leghal Senior Attorney Peter Renn said, "This ban not only wrongfully prevents patriotic, talented Americans from serving, it also compromises the safety and security of our country". Trump has tasked Secretary of Defense Jim Mattis with coming up with a plan by February 2018 for addressing already enlisted transgender individuals.
The president left open the possibility of permitting transgender military service in the future if the Secretary of Defense "provides a recommendation. that I find convincing".
Both lawsuits say the ban violates USA constitutional guarantees of equal protection and due process under the Fifth Amendment.
Friday, President Donald Trump signed an official memo implementing a new policy on "military service for transgender individuals".
The president has echoed a claim from many conservative Republicans that transgender service members disrupt the military's ranks and add medical costs that undermine troop readiness - a cost that LGBT groups say is just a minuscule sliver of the Defense Department's overall health care budget. That was the conclusion of a RAND Corporation study that investigated the matter for the Obama administration, according to the ACLU.
President Trump has signed a memorandum that directs the USA military not to accept transgender men and women as recruits and halts the use of government funds for sex-reassignment surgeries for active personnel unless the process is already underway. Two sought to join the armed forces, and a third is already a serving member.
According to a Rand Corp. study issued past year, there would be "minimal" impacts on readiness, with only 10 to 130 active-duty members having reduced deployability because of gender transition-related treatments, the ACLU's suit says.