South Dakota Gov. Kristi Noem signed a bill that will ban transgender female athletes from participating in girls' or women's school sports.

"This bill's about fairness," the Republican said during a news conference Thursday after signing Senate Bill 46, which will prohibit transgender athletes from competing in girls' sports. "It's about allowing biological females… to compete fairly on a level playing field that gives them opportunities for success."

Noem positioned her signing of the bill as a defense of Title IX, federal civil rights law that prohibits discrimination in school and education programs on the basis of sex.

South Dakota Gov. Kristi Noem (Photographer: Rachel Mummey/Bloomberg via Getty Images)

KRISTI NOEM'S FORMER ADVISER ACCUSED GOVERNOR OF 'GASLIGHTING' WITH NEW AD ON WOMEN'S SPORTS

"Title IX fought for that years and years ago and I've been doing this for years, which started, man, almost five years ago now in the sport of rodeo, where we protected girls’ events," she said of the bill last month.

South Dakota Gov. Kristi Noem (Photo Courtesy of the Committee on Arrangements for the 2020 Republican National Committee via Getty Images)

The push for the legislation comes after the governor controversially vetoed similar legislation last year, sending it back to the legislature with requests to change provisions related to college sports, which she said would be unworkable for organizations that compete on a national level.

But Noem defended that action last month, saying she has worked to put policies in place to "protect girls' sports."

"I did not veto a bill," Noem said. "What I did was, I asked my legislature for changes, and they rejected it. So immediately that very same day I put executive orders in place to protect girls’ sports."

Opponents of last year's bill argued that it could open the state up to lawsuits from the NCAA, jeopardizing the state's ability to hold nationally sanctioned events.

CLICK HERE TO GET THE FOX NEWS APP

South Dakota Gov. Kristi Noem ( Joe Raedle/Getty Images)

But Noem's office signaled optimism that the NCAA would not take adverse action against the state after signing the legislation, citing other states that have taken similar action.

"Governor Noem is confident that the NCAA will not pull events," Noem's Communications Director Ian Fury told Fox News Digital Thursday. "Look at the states with SEC schools that have passed similar legislation – the NCAA has done nothing to threaten their events."