The U.S. Department of Justice on Monday filed an appeal on a court order extending an injunction against President Donald Trump's ban on transgender troops.

In a series of tweets in July, Trump declared that the military will no longer “accept or allow” transgender troops to serve “in any capacity.” Four lawsuits have been filed challenging the ban.

(Related: Trump says military will bar transgender troops.)

Last month, a federal judge in Washington kept in place a hold on the ban. In a 31-page ruling, U.S. District Judge Marsha Pechman said that transgender people represent a “protected class” and that “any attempt to exclude them from military service will be looked at with the highest level of care, and will be subject to the Court's 'strict scrutiny.' This means that before Defendants can implement the Ban, they must show that it was sincerely motivated by compelling interests, rather than by prejudice or stereotype, and that it is narrowly tailored to achieve those interests.”

The DOJ's filing did not provide an explanation for its appeal to the Ninth Circuit Court of Appeals, the Washington Blade reported.

Plaintiffs in the case, nine transgender people who are serving or wish to serve in the military, three groups and the state of Washington, are represented by Lambda Legal and OutServe-SLDN.

Pechman first halted implementation of the ban in a December ruling, saying that the policy “is likely unconstitutional.”

According to the Los Angeles Blade, Pechman refused to issue a permanent injunction in April, which means the case is likely heading to trial.