The Trump administration’s effort to ban transgender personnel from military service will face major tests in the coming months, culminating in a potential Supreme Court decision that could decide whether the Pentagon’s decision process was constitutional, according to organizations representing the troops.

On Dec. 10, the U.S. Court of Appeals for the District of Columbia Circuit will hear government appeals in Doe v. Trump, in which the courts decided that the Pentagon had to comply with previous DoD policy allowing transgender recruits to enlist by Jan. 1, 2018.

More important may be a January Supreme Court deadline. Attorneys representing the transgender plaintiffs have until Dec. 24 to file their response to the White House’s request last week that the Supreme Court take up the transgender military service ban, effectively jumping past all of the lower court proceedings that are still in play.

The Supreme Court would have to decide by Jan. 18 whether it will weigh in during this term. If the court does hear the case, it could set national policy on transgender military service.

However, the Dec. 10 case also has important implications for the military. While the Jan. 1 enlistment deadline has already been decided, the court will now be asked to weigh in on whether President Donald Trump’s July 2017 tweets and subsequent order to Defense Secretary Jim Mattis in August 2017, which were later reflected in the Pentagon’s March 2018 policy memo on transgender service, should be subject to the military deference doctrine in the courts.

Military deference doctrine refers to the the courts' general deference to the military’s decision-making process on national security matters. However, the courts maintain a right to review and weigh into constitutional questions, such as whether a military policy discriminates on the basis of gender or sexual preference.

Plaintiffs attorneys involved in the cases briefed reporters Thursday on the condition they not be named.

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The attorneys said the military’s decisions on transgender service “were based on bias, not military judgment,” and were driven directly by the president’s tweets. Since the ban was first announced, every service chief has stated publicly that having transgender personnel in the ranks does not negatively affect military readiness.

If the court finds the March 2018 memo is separate and should be subject to military deference, the attorneys said they worry it will expand the number of issues the military can shield from legal challenge.

As Doe v. Trump has progressed, government lawyers have argued it is Mattis’ 2018 memo that should be under consideration, not the tweets nor Trump’s direct August 2017 order to the Pentagon. In the latest filing available to the public, government lawyers have asked the court to quickly separate the two, so the March 2018 memo can be fully implemented. Further delay, they said, would harm military readiness.

In their request to the Supreme Court to hear the cases, government attorneys argued that Mattis’ decision reflected an “extensive process of consultation” and that a ruling against the administration and Pentagon would undermine “an issue of imperative public importance: the authority of the U.S. military to determine who may serve in the Nation’s armed forces.”

Amanda Johnston, a spokeswoman for GLBTQ Legal Advocates & Defenders said the government has provided no proof that transgender service negatively impacts military readiness. In addition, transgender service members have enlisted since Jan. 1, and hundreds are currently serving openly, with no apparent impact, she said.

“Every single day that goes by with transgender service members serving undermines their case,” Johnston said.