The lawsuit was filed just days after President Trump formally ordered the Pentagon to ban the recruitment of openly transgender people and to determine whether transgender people already serving should be allowed to remain.
The second lawsuit was filed in Seattle federal court by Lambda Legal and OutServe-SLDN.
When Trump announced his intentions to reinstate a ban, the Pentagon was still deliberating its position on transgender people wishing to enlist. "The president claims in tweets transgender service costs money and military readiness".
Trump claimed he had consulted with "generals and military experts" and decided the "United States Government will not accept or allow Transgender individuals to serve in any capacity in the U.S. Military".
Both lawsuits argue the ban violates the Fifth Amendment, which guarantees equal protection and substantive due process.
Trump issued a memorandum on Friday afternoon ordering a reversal of Obama administration rules that had started to let transgender people to serve openly in the military. These advocates also argue that the federal and state government must support people who say they are "transgender" by requiring other people to treat them as members of the opposite sex and to refer to them with opposite-sex pronouns. "Our military must be focused on the decisive and overwhelming victory and can not be burdened with the tremendous medical costs and disruption that transgender in the military would entail".More news: It's official, and DeShone Kizer is Browns quarterback
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He added that allowing men and women who are transgender "to serve openly" and providing them with necessary healthcare "does nothing to harm military readiness or unit cohesion".
According to a Rand Corp. study issued a year ago, 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.
"The Secretaries only have a narrow window of discretion to decide the individual fates of now serving transgender personnel, who in the best case would be permitted to serve under separate standards that apply only to them, under a general presumption that they are unfit to serve, and with no assurance that their permission to remain will endure", the memo says. Also named in the ACLU lawsuit are each of the civilian heads of the military departments.
The lawsuits may be undermined by Trump's decision to give Mattis authority to decide on a case-by-case basis whether to exempt some soldiers from the ban, said Thomas Spoehr, director of the Heritage Foundation's Center for National Security.
White House officials said Monday that they do not comment on pending litigation.
Renn's lawsuit is filed in the US District Court for the Western District of Washington.