This just happened. The Obama administration alleges the state is violating the Civil Rights Act:

Could this happen here? Yes. Last week, a report by the Williams Institute warned that Washington could lose $4.46 billion in annual federal funding if it passes Initiative “Just Want Privacy” 1515, an initiative that would overturn provisions of the state’s human rights code which ensure transgender people can use the bathroom of their gender identity—precisely because the initiative violates the Civil Rights Act:

“If I-1515 is passed, it would explicitly require that restrooms are gender segregated by biological sex, which is in direct contradiction with Title IX,” Amira Hasenbush, one of the authors of the report, told The Stranger. “So that would be a direct conflict, and schools can be denied federal funding if they’re in conflict with Title IX and Title VII.”

UPDATE: Loretta Lynch just gave an extraordinary speech addressing the transgender community: “We see you, we stand with you and we will do everything we can to protect you going forward. … History is on your side.”