Unconstitutional.
Title IX is the most commonly used name for the landmark federal civil rights law in the United States that was enacted as part (Title IX) of the Education Amendments of 1972. It prohibits sex-based discrimination in any school or any other education program that receives funding from the federal government.
https://en.m.wikipedia.org/wiki/Title_IX
You are correct. We could argue all day about gender identity but that misses the point since it’s a law passed by Congress.
Joe’s not free to make his own laws and call them “rules”.