In a surprising move overshadowed by the Super Tuesday primaries, the governor of South Dakota vetoed a bill preventing students who claim to be “transgender” from using the bathrooms or locker rooms of the opposite sex. Though a Republican, Gov. Dennis Daugaard rejected a bill passed by super-majorities in the Republican-controlled state house and senate. The law would have been the first in the nation. He had to sign or veto the bill by the end of the day or it would have automatically become law.

The bill defined sex as “the physical condition of being male or female as determined by a person’s chromosomes and anatomy as identified at birth,” and ordered schools to make “reasonable accommodation” to transgender students.

In his veto message, the governor said that the bill “does not address any pressing issue concerning the school districts of South Dakota” and argued that “It removes the ability of local school districts to determine the most appropriate accommodations for their individual students and replaces that flexibility with a state mandate.”

Further, he continued, the bill “openly invites federal litigation” and “will create a certain liability for school districts and the state in an area where no such liability exists today.” The American Civil Liberties Union had already threatened to encourage students who felt themselves harmed to complain to the Department of Education’s Office of Civil Rights, and promised to represent them. The director of the state branch of the ACLU also raised the possibility of lawsuits against the state challenging the constitutionality of the law.

Supporters of the bill defended it as a response to the Obama administration’s claim that preventing transgender students from using the facilities they choose violates Title IX.