“Every district attorney in the state is going to be empowered to potentially investigate miscarriages to test the limits of the law and see if they can put doctors in prison,” said State Senator Kelda Roys, a Democrat in Wisconsin. “It makes things very difficult for health care providers. It unleashes a whole host of terrible circumstances.”

The sudden importance of laws that were written before women had the right to vote has sent legislators, activists and abortion providers scrambling to understand the implications. In Wisconsin, clinics in Milwaukee and Madison had already paused scheduling appointments for abortion procedures next week in anticipation of the Supreme Court ruling; after its decision came on Friday morning, all of the state’s clinics stopped providing abortions entirely.

Ismael Ozanne, the Dane County district attorney, signaled on Friday that he would not enforce the Wisconsin law that criminalized abortion, a suggestion that a patchwork situation could develop in which abortion is prosecuted differently from county to county.

According to the Guttmacher Institute, which supports abortion rights, eight states still have abortion bans on the books that predate Roe v. Wade, but some have more recent bans that would most likely take precedence. In recent years, states including New Mexico, Vermont and Massachusetts have removed old bans.

In Michigan, where a law from 1931 bans abortion, the battle is already playing out in the courts. Gov. Gretchen Whitmer, a Democrat, filed a lawsuit in April asking the Michigan Supreme Court to resolve whether the State Constitution protects the right to abortion. A Michigan judge issued an injunction in May that stops the ban from being enforced, at least temporarily, until a separate lawsuit is resolved.

On Friday, Ms. Whitmer called the 1931 law “antiquated,” noting that it does not provide exceptions for rape or incest. “The 1931 law would punish women and strip away their right to make decisions about their own bodies,” she said in a statement.

Ms. Whitmer has vowed to veto legislation that would restrict abortion. The Michigan Legislature has a Republican majority but not one large enough to be likely to override a veto.

There is also a pre-Roe ban in West Virginia, but experts said it was unclear whether that or newer state laws that put fewer restrictions on abortion would take effect. The state’s attorney general, Patrick Morrisey, said in a statement on Friday that he would soon “be providing a legal opinion to the Legislature about how it should proceed to save as many babies’ lives as humanly and legally possible.”

Arizona, Alabama and North Carolina also have older abortion laws on the books, but more recent restrictions passed in those states could take precedence, such as a total ban on abortion that became law in Alabama in 2019 but was superseded by Roe until now.

In Wisconsin, both sides are preparing for lawsuits and political battles over whether the abortion ban, which has been unenforceable since Roe v. Wade made abortion legal in 1973, will result in prosecutions.

“The future of this old law will be determined in our state courts and our state political system,” said Mike Murray, the vice president of government and external affairs for Planned Parenthood of Wisconsin. “On a practical level, there is going to be litigation requesting clarification from our state courts about whether or not the 1849 law is enforceable.”

Gracie Skogman, the legislative director for Wisconsin Right to Life, said she hoped the 1849 law “is enforceable and saves lives here in Wisconsin, but we also do expect that there will be legal challenges.” On Friday, the organization said “Wisconsin is in powerful position to defend preborn life due to our pre-Roe statute.”

Under the ban in Wisconsin, doctors who perform abortions can be found guilty of a felony. It includes exceptions for an abortion that is necessary to save the mother’s life, but does not make exceptions for cases of rape or incest.

Laws banning abortion in the 19th century were typically the result of an effort to regulate how medicine was practiced, which medicines could be distributed and who was providing drugs that could cause abortion, historians said. The laws tended to ban abortion only after “quickening” — a point about midway through pregnancy when a woman can feel a fetus move in the womb.

James Mohr, a professor at the University of Oregon whose book “Abortion in America” details the history of abortion in the United States, said 19th-century laws banning abortion were passed not for political reasons, but because of pressure from elite physicians, who were concerned that people who called themselves doctors were performing abortions without training.

“It’s very hard for Americans to wrap their mind around the fact that abortion was simply not a public issue in the 19th century,” he said. “It was not discussed in public, it was not political, it was not politicized.”

After states passed abortion bans, he said, “It would appear that the practice of abortion continued just about the way it always had.”

“The same number of pregnancies as a percentage continued to be terminated,” he continued. “Prosecutors almost never brought prosecutions under these laws because juries wouldn’t convict.”

Lauren MacIvor Thompson, an assistant professor of history and interdisciplinary studies at Kennesaw State University in Georgia who studies abortion history, said that recent laws banning abortion were far more restrictive than those passed well over a century ago.

“By and large, many of the laws passed in the 19th century were more lenient and often did not punish the woman,” she said. “That is shifting rapidly.”

Past efforts to repeal the 1849 law in Wisconsin have fizzled, even when the Democratic Party controlled both the governor’s office and the Legislature, and there was little push from the public to overturn it.

“I hadn’t heard much about the ban until quite recently,” said Jenny Higgins, a professor of gender and women’s studies and obstetrics and gynecology at the University of Wisconsin-Madison School of Medicine and Public Health. “Folks didn’t really believe that overturning Roe was possible, or palatable, until recently.”

Wisconsinites have indicated in recent polls that they favor keeping abortion legal. In a recent poll conducted by Marquette Law School, 58 percent of state residents said abortion should be legal in all or most cases.

This past week, Gov. Tony Evers convened a special session in the Legislature to pressure lawmakers to repeal the abortion ban. A ring of protesters in pink shirts gathered at the Statehouse in Madison, their chants ricocheting under the dome of the Capitol building.

But Republicans, who hold a majority in the State Senate, ended the session almost as quickly as it began, without a vote or discussion. Robin Vos, the speaker of the Assembly, posted on Twitter on Friday that “safeguarding the lives of unborn children shouldn’t be controversial.”

Mr. Evers, who is running for re-election in November, condemned the Republican lawmakers after the session, saying they had jeopardized access to health care.

“Republicans’ refusal to act will have real and severe consequences for all of us and the people we care most about who could see their ability to make their own reproductive health care decisions stripped away from them,” Mr. Evers said in a statement.