Arizona’s highest court reinstated an 1864 law that bans nearly all abortions, a decision that could have far-reaching consequences for women’s health care and election-year politics in a critical battleground state.

Here’s what to know about the ruling, the law and its possible impact.

What is the 1864 law?

The law, which was on the books long before Arizona achieved statehood in 1912, outlaws abortion from the moment of conception, except when necessary to save the life of the mother, and it makes no exceptions for rape or incest. It bans all types of abortions, including medication abortions.

Until now, abortion had been legal in Arizona through 15 weeks of pregnancy. Since the overturning of Roe v. Wade nearly two years ago, supporters and opponents of abortion rights in Arizona had been fighting in court over whether the 1864 law, which had sat dormant for decades, could be enforced, or whether it had been effectively neutered by decades of other state laws that regulate and restrict abortion.

Doctors prosecuted under the law could face fines and prison terms of two to five years for providing, supplying or administering care to a pregnant woman.

What does the ruling say?

On April 9, the Arizona Supreme Court ruled in a 4-to-2 decision that the pre-statehood law was “now enforceable.”

The court said that because the federal right to abortion had been overturned by the U.S. Supreme Court in 2022, there was no federal or state law preventing Arizona from enforcing the near-total ban. It noted that the State Legislature had not created a right to abortion when it passed the 15-week ban in 2022.

“Physicians are now on notice that all abortions, except those necessary to save a woman’s life, are illegal,” the court wrote.

You can read the full ruling here.

Is the law in effect now?

No. The court put its ruling on hold for 14 days, and sent the case back to a lower court to hear additional arguments about the law’s constitutionality.

Because of this 14-day pause, and an additional 45-day delay before enforcement, it will very likely be weeks before the law goes into effect. Abortion providers said they expected to continue performing abortions through May.

It is also unclear what the enforcement of the law will look like. Arizona’s attorney general, Kris Mayes, a Democrat, called the ruling “unconscionable and an affront to freedom,” and said she would not prosecute doctors for providing abortions, potentially opening a new legal fight with Republican prosecutors and abortion opponents.

But the ruling could prompt clinics in the state to stop providing abortions and women to travel to nearby states like California, New Mexico or Colorado to end their pregnancies.

Could the ban be overturned?

Yes. In the majority opinion, the concurring justices said that a “policy matter of this gravity must ultimately be resolved by our citizens through the legislature or the initiative process.”

State legislators could repeal the ban or voters could overturn it in November, if abortion rights groups succeed in placing a measure on the ballot enshrining abortion protections into the State Constitution.

State Senator T.J. Shope, a Republican who represents a suburban and rural area south of Phoenix, said he would work to repeal the 1864 ban but leave in place the 15-week prohibition that was signed into law by the previous governor, Doug Ducey, a Republican.

The former governor denounced the ruling, saying that it was “not the outcome I would have preferred.” He called on Arizona’s elected leaders to “heed the will of the people and address this issue with a policy that is workable and reflective of our electorate.”

The proposed ballot measure would enshrine abortion access until “fetal viability,” or about 24 weeks, in the State Constitution, returning to the standard set by Roe. The effort needs close to 400,000 signatures by July to get on the ballot. The coalition working on the measure, Arizona for Abortion Access, said it had already exceeded the threshold.

How could this affect the 2024 election?

The stakes of this ruling could be significant for races up and down the ballot in Arizona this fall.

President Biden and Democratic officials have blamed former President Donald J. Trump for the dwindling access to abortion care in America. On April 8, Mr. Trump said that abortion rights should be left up to the states.

Democrats, who seized on abortion to win campaigns for Arizona governor and attorney general in the 2022 midterm elections, said the issue of reproductive rights would galvanize their supporters.

Representative Ruben Gallego, running unopposed in the Democratic primary for Senate, criticized the ruling and tied it to his opponent, Kari Lake, who called the near-total ban a “great law” when she was running for governor in 2022.

Ms. Lake has been emblematic of a Republican shift on abortion. She came out against a federal ban last year while still backing Arizona’s 15-week restriction, and said on April 9 that it was “abundantly clear that the pre-statehood law is out of step with Arizonans.”

Representatives Juan Ciscomani and David Schweikert, two Republicans facing re-election challenges in closely divided districts, also criticized the ruling and urged state lawmakers to address it.

Where else is abortion illegal?

Twenty-one states currently ban or restrict abortion earlier in pregnancy than what Roe v. Wade established.

Reporting was contributed by Jack Healy, Kellen Browning, Lisa Lerer, Aishvarya Kavi and Chris Cameron.