Trump's controversial transgender troop ban takes effect

U.S President Donald Trump's controversial ban on transgender Americans in the military comes into force on Friday following a protracted legal battle.

Trump's administration has insisted that there is 'too great a risk to military effectiveness and lethality' to allow transgender people to serve -- reversing a policy enacted under his predecessor Barack Obama.

The Pentagon says the restrictions are not a blanket ban, but they would bar many if not most people who identify as transgender from enlisting in America's armed forces.

The policy -- which has undergone various iterations since Trump first announced it on Twitter in July 2017 -- has been widely criticized by rights activists and has been repeatedly challenged in court.

The U.S Supreme Court ultimately ruled in January that the policy could take effect pending the outcome of ongoing litigation.

Under the latest version of Trump's policy, no one who has transitioned to another gender, been diagnosed with 'gender dysphoria' or who requires hormone treatment will be able to enlist.