US President Donald Trump has signed an order to ban most trans people from military service.

The memorandum bans “transgender persons who require or have undergone gender transition”, but allows the Pentagon and other agencies some discretion, BBC News has reported.

Activists last year filed a lawsuit challenging the ban, after Trump tweeted an announcement that trans people would not be allowed to serve.

“Trump’s directive to exclude transgender people from military service has created a tidal wave of harms that have already been felt throughout our armed services,” said Shannon Minter, legal director of the National Centre for Lesbian Rights, at the time.

“Transgender service members have been blindsided by this shift and are scrambling to deal with what it means for their futures and their families.”

The blanket ban on trans people was overruled by federal judges.

Judge Colleen Kollar-Kotelly of the Federal District Court for the District of Columbia ruled that it had been based on “disapproval of transgender people generally”.

Calls by trans people to suicide hotlines reportedly doubled last year after Trump’s initial tweet announcing the ban.

An estimated 4,000 to 10,000 US troops are trans.

The new policy allows existing trans military personnel to continue serving if their gender dysphoria was diagnosed after the Obama administration’s policy of trans inclusion took effect.

US House Democratic Leader Nancy Pelosi called the new policy “the same cowardly, disgusting ban the president announced last summer”, adding it was intended to “humiliate” trans people.

The American Civil Liberties Union said called it “transphobia masquerading as policy”, saying that it was not evidence-based but “reverse-engineered for the sole purpose of carrying out President Trump’s reckless and unconstitutional ban”.

When the order will take effect to ban trans people from military service is yet unknown, and it is expected to face legal challenges.

© Star Observer 2017 | For the latest in lesbian, gay, bisexual, trans* and intersex (LGBTI) news in Australia, be sure to visit starobserver.com.au daily. You can also read our latest magazines or Join us on our Facebook page and Twitter feed.