Supreme Court Allows Trump's Transgender Military Ban The vote was 5 to 4. The ban will be temporarily in effect while the case moves forward in the lower courts. The policy prohibits people to serve in the military if they identify with a gender different from their biological sex. There are exceptions for those already serving openly and for others willing to serve “in their biological sex.” The policy was first announced by President Trump on Twitter in July 2017. President Trump, via Twitter The policy was officially announced by James Mattis, Secretary of Defense at the time, in 2018. Carla Gleason, Pentagon spokesperson, via CNN