PIERRE, S.D. — South Dakota’s governor vetoed a bill Tuesday that would have made the state the first in the U.S. to approve a law requiring transgender students to use bathrooms and locker rooms that match their sex at birth.

Republican Gov. Dennis Daugaard, who initially reacted positively to the proposal but said he needed to research the issue, rejected the bill after groups such as the American Civil Liberties Union and the Human Rights Campaign insisted it was discriminatory.

In his veto message, Daugaard said the bill “does not address any pressing issue” and that such decisions were best left to local school officials. He also noted that signing the bill could create costly liability issues for schools and the state. The ACLU had promised to encourage legal action if the bill became law.

“I am so happy right now. You have no idea,” said 18-year-old Thomas Lewis, a transgender high school student in Sioux Falls. Lewis said he has support at his school, but that the veto shows such support goes beyond his friends.

“The government’s not going to hold me back from who I really am,” he said.

The bill’s sponsor, Republican Rep. Fred Deutsch, said he would ask lawmakers not to override the veto, saying more focus on the issue would detract from the Legislature’s accomplishment this year. The Republican-controlled Legislature approved the bill last month, with supporters saying it would protect student privacy.

Transgender rights have become a new flashpoint in the nation’s cultural clashes following the landmark U.S. Supreme Court ruling that legalized same-sex marriage last year. The high court victory encouraged advocates for lesbian, gay, bisexual, and transgender rights to push harder, prompting backlash from conservatives.

Caitlyn Jenner, the transgender activist and former Olympic decathlon gold medalist, had called on Daugaard to veto the bill. Opponents also used the South Dakota Tourism Department’s Twitter hashtag to take aim at the state’s roughly $3.8 billion tourism industry.