A federal judge on Monday ruled that the government must allow transgender people to enlist in the military beginning on Jan. 1, 2018.

The order came after the government asked Washington, D.C., District Court Judge Colleen Kollar-Kotelly if it could push back the Jan. 1 enlistment date, which was established under President Barack Obama.

Last month, Kotar-Kelly issued a preliminary injunction that blocked the Trump administration's plans to exclude transgender people from the military. She said the government had offered no solid evidence that showed why the ban was necessary.

“This is an important clarification because it means the military can’t do an end run around the judge’s decision,” said Jennifer Levi, of the GLBTQ Legal Advocates & Defenders, or GLAD, said about Monday's order.

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GLAD and The National Center for Lesbian Rights represent the five longtime transgender military service members who sued the government in August, claiming that Trump’s efforts to ban transgender people from military service was unconstitutional and denied them equal rights and due process.

Trump announced his decision to end transgender military service in a series of tweets in July. In an August memo, he told the Defense Department to extend an indefinite ban, and ordered Defense Secretary Jim Mattis to determine “how to address” current service members within six months.

A Justice Department spokeswoman did not immediately respond to a request for comment. A Defense Department spokesperson could not immediately be reached.

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In a separate case, a federal judge in Baltimore last week also issued a preliminary injunction on the ban, saying that the six plaintiffs who filed that suit had demonstrated its harmful impact.

That judge, Marvin Garbis, said that a "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."

A that time, a Justice Department spokeswoman, Lauren Ehrsam, told the Associated Press that the injunction was “premature” because the Pentagon “is actively reviewing” transgender service requirements.

Ehrsam added that “none of the plaintiffs have established that they will be impacted by current policies on military service."