The U.S. Supreme Court on Tuesday permitted Donald Trump's administration to implement his ban on transgender personnel in the military, one of a series of directives by the Republican president to curb transgender rights.

In a decision that could trigger the discharge of thousands of current personnel, the court granted the Justice Department's request to lift a federal judge's nationwide order blocking the military from carrying out Trump's prohibition on transgender service members while a legal challenge to the policy plays out.

Seattle-based U.S. District Judge Benjamin Settle found that Trump's order likely violates the U.S. Constitution's Fifth Amendment right to equal protection under the law.

Trump signed an executive order in January after returning to the presidency that reversed a policy implemented under his Democratic predecessor Joe Biden that had allowed transgender troops to serve openly in the American armed forces.

Trump's directive cast the gender identity of transgender people as a lie and asserted that they are unable to satisfy the standards needed for service in the American armed forces.

"A man's assertion that he is a woman, and his requirement that others honor this falsehood, is not consistent with the humility and selflessness required of a service member," Trump's directive stated.

The Pentagon later issued guidance to implement Trump's order, disqualifying from military service current troops and applicants with a history or diagnosis of gender dysphoria or who had undergone gender transition steps. The guidance allowed people to be considered for a waiver on a case-by-case basis if their service would directly support "warfighting capabilities."

Gender dysphoria is the clinical diagnosis for significant distress that can result from an incongruence between a person's gender identity and the sex they were assigned at birth.

During his first term as president, Trump also took aim at transgender military personnel with a more limited restriction. The Supreme Court in 2019 allowed the Defense Department to enforce Trump's transgender military prohibition that had let certain personnel diagnosed with gender dysphoria after entering the military to continue to serve.

The lawsuit against the new policy was filed by seven active-duty transgender troops, a transgender man seeking to enlist and a civil rights advocacy group.

Settle blocked Trump's policy, calling it "unsupported, dramatic and facially unfair," and saying that the administration had provided no evidence of any harm that had resulted from the inclusion of transgender people in the armed services.

Transgender rights are a flashpoint in the U.S. culture wars. Trump has targeted the rights of transgender people in a series of executive orders including one stating that the U.S. government will recognize only two sexes, male and female, and that they are "not changeable."

Trump also signed an order to end federal funding or support for healthcare that aids the transition of transgender youth and another one attempting to exclude transgender girls and women from female sports.

In the military ban case, the Justice Department had told the Supreme Court that Settle had usurped the authority of the executive branch of government - headed by Trump - to determine who may serve in the armed forces. The judge's injunction "cannot be squared with the substantial deference that the (Department of Defense's) professional military judgments are owed," the Justice Department said in a court filing.

The plaintiffs had urged the justices to maintain the block on Trump's ban.

The San Francisco-based 9th U.S. Circuit Court of Appeals declined the administration's request to put Settle's order on hold.

The Supreme Court is expected to rule in a major transgender rights case by the end of June. The justices heard arguments on December 4 over the legality of a Republican-backed ban in Tennessee on gender-affirming medical care for transgender minors.