Yana Paskova / Getty Images

Defining gender as strictly male or female, and unchangeable over time, would effectively erase many trans and gender-nonconforming individuals.

According to the New York Times, the memo from last spring came from the US Department of Health and Human Services, which proposed changes in the way sex is defined under federal laws like Title IX. Title IX, however, doesn't fall under HHS's purview, and the scope of the proposal remains unclear.