The United States Supreme Court has allowed President Donald Trump to enforce his policy of banning certain transgender people from the military.
The court voted 5-4 to grant a Trump administration request to lift injunctions blocking the policy while challenges continue in lower courts.
The four liberal judges on the court opposed the ruling.
The policy prohibits "transgender persons who require or have undergone gender transition" from serving.
The Trump administration had also appealed for an expedited ruling on the case, which the Supreme Court declined to take up.
The president announced on Twitter in 2017 that the country would no longer "accept or allow" transgender Americans to serve in the military, citing "tremendous medical costs and disruption".
Former defence secretary Jim Mattis refined the policy to limit it to transgender individuals with a history of gender dysphoria, or when a person's biological sex and identity does not match.
He said the new policy would make exceptions for several hundred transgender people already serving openly or willing to serve "in their biological sex".
There are currently some 8980 active duty transgender troops, according to Department of Defence data analysed by the Palm Center, a public policy nonprofit.
Mr Mattis in his memo argued that "by its very nature, military service requires sacrifice," and that those who serve "voluntarily accept limitations on their personal liberties".
The move is a reversal of an Obama administration policy that ruled transgender Americans could serve openly in the military as well as obtain funding for gender re-assignment surgery.