Here's what you need to know about a piece of legislation passed in the Oklahoma House and Senate May 19 that would have made it illegal for doctors to perform abortions that weren't necessary to save the life of the mother. (Sarah Parnass/The Washington Post)

Oklahoma Gov. Mary Fallin vetoed a controversial bill Friday that would have made it a felony for doctors to perform abortions, saying she felt the bill was too vague and unable to withstand a legal challenge.

Fallin’s decision came a day after lawmakers in the state approved the unprecedented bill, well before a deadline for her to sign the measure, veto it or allow it to become law without her signature. The bill would have also barred physicians who participated in abortions from getting medical licenses, though it allowed an exception for doctors performing abortions deemed necessary to save the mother’s life.

“The bill is so ambiguous and so vague that doctors cannot be certain what medical circumstances would be considered ‘necessary to preserve the life of the mother,’” Fallin, a Republican, said in a statement announcing her decision.

According to the measure, known as SB1552, a person who performs or induces an abortion — dubbed “unprofessional conduct” — would have been found guilty of a felony and punished with between one and three years in the state penitentiary.

In a message to lawmakers, Fallin said that while she has “signed no less than 18 bills supporting pro-life and pro-family values,” she was critical of this bill’s provision making it a felony to perform an abortion.

Fallin said that she supported “a re-examination” of the Supreme Court’s landmark 1973 decision in Roe v. Wade, which recognized a woman’s right to an abortion, but she felt this was not the right bill to achieve that task.

“In fact, the most direct path to a re-examination of the United States Supreme Court’s ruling in Roe v. Wade is the appointment of a conservative, pro-life justice to the United States Supreme Court,” Fallin said in a statement.

Oklahoma Governor Mary Fallin, left, speaks during a bill signing for a bill requiring doctors in Oklahoma to check a new prescription drug database before prescribing certain addictive drugs, in Oklahoma City, Tuesday, March 31, 2015. It the first bill Fallin has signed this legislative session, and it will take effect Nov. 1. (AP Photo/Sue Ogrocki) Oklahoma Gov. Mary Fallin announced her decision on Friday. (Sue Ogrocki/AP)

The Oklahoma bill is the first such measure of its kind, according to the Center for Reproductive Rights, which says that other states seeking to outlaw abortion have simply tried to ban the procedure rather than attach penalties like this.

“Governor Fallin did the right thing today in vetoing this utterly unconstitutional and dangerous bill,” Nancy Northup, president and chief executive of the center, said in a statement. “But the reality is countless Oklahoma women still face incredible obstacles to access safe and legal abortion when they’ve made the decision to end a pregnancy.”

There are only two abortion clinics in Oklahoma, according to the Center for Reproductive Rights.

Trust Women, an organization based in Kansas, says it is opening another clinic in Oklahoma City this summer. Julie A. Burkhart, the group’s founder and chief executive, said in a statement that despite the veto, she believes Fallin’s views on abortion remain the same and that “Oklahoma continues to be a politically hostile environment for women and their families.”

Abortion rights groups had described the bill as dangerous and decried it for penalizing doctors. Fallin had until next Wednesday to make a decision on the legislation, and she had not previously given any public indication of what she would do.

State Sen. Nathan Dahm, a Republican who represents Tulsa County, had said he hoped the measure would lead to Roe v. Wade being overturned. After Fallin announced her veto Friday, Dahm told the Associated Press that he was considering whether to push for an override of the governor’s veto. Dahm did not respond to multiple messages seeking comment Thursday and Friday.

It would take a two-thirds vote by each house in Oklahoma’s legislature to override Fallin’s veto.

Liberty Counsel, a group that rose to national prominence last year defending the Kentucky clerk who refused to sign same-sex marriage licenses, said Friday that it had supported the legislation in Oklahoma and had vowed to defend it in court.

Mat Staver, the group’s founder and chairman, said in an interview Friday he was “shocked” by Fallin’s decision. Staver called it a betrayal because he said he had met with the governor last year to discuss the proposal and that she gave it her approval.

Michael McNutt, a spokesman for Fallin, said that the governor does not commit to legislation until she sees a final version because bills may change during the legislative process. On Thursday, after the measure was sent to Fallin, McNutt said the governor could not immediately comment on it until she and her staff had a chance to review this final version.

Staver said that he hoped lawmakers would override Fallin’s veto, adding that Liberty Counsel remained ready to defend the measure in court.

“This particular bill puts a target on Roe v. Wade,” Staver said Friday. “It is Oklahoma’s line in the sand on the sanctity of human life, as standing on the side of protecting innocent children.”

The Oklahoma State Medical Association, which had opposed the measure and called it “one more insulting slap in the face of our state’s medical providers,” praised Fallin’s decision on Friday.

“This bill would have, in a very unprecedented way, made … the performance of a legal medical procedure a criminal act,” Sherri Baker, the group’s president and a pediatric cardiologist, said in an interview. “We are very pleased and very grateful for Governor Fallin for her leadership today.”

Further reading:

The forgotten history of Justice Ginsburg’s criticism of Roe v. Wade

This is a developing story. First published: 5:03 p.m.