The Department of Defense is ready to put the Trump administration’s policy barring transgender people from serving in the military into effect.

A memo obtained Tuesday by the Associated Press outlines how the ban will be put into effect, including discharging and denying enlistment to transgender individuals.

The policy, which was signed by acting Deputy Defense Secretary David Norquist, says that those who wish to serve in the military must serve as the gender they were assigned at birth.

The policy will go into effect in 30 days.

According to the Advocate , implementing the policy would include discharging about 13,700 members already serving. The AP notes that there are 14,700 service members who identify as transgender, but not all of them seek treatment.

After April 12, anyone taking hormones or who has transitioned will not be allowed to enlist.

The memo says that a service member can be discharged when diagnosed with gender dysphoria if the person is “unable or unwilling to adhere to all applicable standards, including the standards associated with his or her biological sex, or seeks transition to another gender.”

In 2016, the Obama administration announced that transgender people already serving in the military would be allowed to serve openly.

When Trump took office, he announced that trans people would not be allowed to serve “in any capacity.”