A federal judge on Monday rejected President Donald Trump's request to further delay the ability of transgender people to enlist in the military, and the Pentagon said enlistments would begin on Jan. 1.

“Having carefully considered all of the evidence before it, the Court is not persuaded that Defendants will be irreparably injured by allowing the accession of transgender individuals into the military beginning on January 1, 2018,” Judge Colleen Kollar-Kotelly of the U.S. District Court for the District of Columbia wrote in her decision.

The Department of Defense sent a statement to NBC News late Monday afternoon confirming it will comply with recent court orders regarding transgender military recruits.

"As required by recent federal district court orders, the Department of Defense recently announced it will begin processing transgender applicants for military service on January 1, 2018. This policy will be implemented while the Department of Justice appeals those court orders,” the statement read.

"The United States District Court for the District of Columbia ordered DoD to implement, effective January 1, 2018, the accession policy issued by former Secretary Carter in 2016. DoD and the Department of Justice are actively pursuing relief from those court orders in order to allow an ongoing policy review scheduled to be completed before the end of March," the statement continued.

Kollar-Kotelly ruled against Trump's transgender military ban in October, saying the administration had provided no solid evidence for why a ban should be implemented. Another federal judge, Marvin Garbis, of U.S. District Court in Maryland, ruled against the ban last month. In a strongly-worded passage from his 53-page decision, Garbis wrote that the "capricious, arbitrary, and unqualified tweet of new policy does not trump the methodical and systematic review by military stakeholders qualified to understand the ramifications of policy change."

The tweet Garbis referred to came in an unexpected series of posts Trump made in July announcing his intention to ban transgender people from serving in the military.

Shannon Minter, legal director for the National Center for Lesbian Rights (NCLR), which, along with GLBTQ Legal Advocates & Defenders (GLAD), has been fighting the transgender military ban in court, applauded Kollar-Kotelly's decision on Monday and shot back at the Trump administration.

“Trump administration claims that our highly sophisticated military is unprepared to implement a minor policy change after more than a year of preparation are simply not credible,” Minter said in a statement to NBC News.

“The military has studied this issue extensively and determined that permitting qualified transgender people to enlist and serve will only strengthen our nation’s armed forces," Minter added. "This administration’s claim that allowing transgender people to enlist will lessen military preparedness is contradicted by the military’s own conclusions."

Amanda Simpson, a former deputy assistant secretary of defense who was the highest-ranking transgender person in the department, said, “The idea there needed to be an emergency stay was ridiculous.”

She also blasted the Trump administration for putting currently serving transgender people and prospective recruits in limbo.

“Young people enlist in our military with the knowledge or at least the promise to serve our country, to pledge their life in service and protection of our nation, and in doing so, they sign a contract that says for a certain number of years they will make that obligation, and they arrange their lives accordingly,” Simpson said. “So now you’re saying, 'Enlist, but there’s a possibility somewhere down the road … we may ask you to leave because we don’t believe trans people can be integrated with our forces'? That’s entirely bogus.”

Potential transgender recruits will have to meet a lengthy and strict set of physical, medical and mental conditions that make it possible, though difficult, for them to join the armed services. Eastburn, the Pentagon spokesman, said transgender recruits will be able to enlist if a medical provider certifies they've been clinically stable in their preferred sex for 18 months and are free of significant distress or impairment in social, occupational or other important areas.

The requirements make it challenging for transgender recruits, but they mirror concerns President Barack Obama's administration laid out when the Pentagon initially lifted its ban on transgender service last year.

"Due to the complexity of this new medical standard, trained medical officers will perform a medical prescreen of transgender applicants for military service who otherwise meet all applicable applicant standards," Eastburn said.

Estimates of trans people currently serving in the military range from just a few thousand to up to 15,000. Amid the political back-and-forth about whether trans people will be able to serve openly, Simpson sent a message to those now serving.

"We’ve got your back, and we’re fighting for you," she said. "You’ve been fighting for us, and all the American people understand the commitment and sacrifice you are making, and we will make sure you have the ability to continue to serve honorably and with distinction."

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