Today, we filed an Amicus brief in the Fifth Circuit supporting a challenge brought by Louisiana, Mississippi, Montana and Idaho to the U.S. Department of Education’s April 29, 2024 Final Rule. That Rule expanded the meaning of the Title IX ban on discrimination “on the basis of sex” to include discrimination on the basis of “sex stereotypes, sex characteristics, sexual orientation, and gender identity.” Our brief argued that the Rule destroys personal privacy for women and girls; destroys women’s and girls’ sports; and censors the free speech rights of teachers and students. We argue that the Supreme Court’s Bostock decision should neither control nor inform a decision in this case. Finally, we point out that the DOE Rule presupposes that biological sex is not an immutable reality, but rather a social construct, changeable at will.