The judge's "strongly worded" opinion pointed out that Trump's new policies likely violated the equal protection clause of the Constitution: “a number of factors — including the sheer breadth of the exclusion ordered by the directives, the unusual circumstances surrounding the President’s announcement of them [he tweeted it out in July, surprising the military], the fact that the reasons given for them do not appear to be supported by any facts, and the recent rejection of those reasons by the military itself — strongly suggest that Plaintiffs’ Fifth Amendment claim is meritorious.”
The plaintiffs? Yes, a group of five transgender women serving in the Coast Guard, Army, and Air Force brought the lawsuit. According to Dave Phillips, "Many of the women had served for years as men and had been deployed to war zones before coming out to commanders when the [transgender] ban was lifted in 2016 [by President Obama]. One is a few years from retirement, according to court documents. Another told her commander she wanted to keep serving, but would resign if the military moved to forcibly discharge her."
Judge Kollar-Kotelly, incidentally, was first appointed to the bench by President Ronald Reagan.