U.S. Supreme Court Justice Anthony Kennedy’s retirement could mean the end of Roe v. Wade if President Donald Trump holds true to his promise to appoint justices willing to overturn the ruling that guaranteed the right to legal abortion. Doing so could leave abortion access in the hands of individual states—and many are poised to ban the procedure entirely.

“Whether women have a right to abortion will depend on which state they live in,” said Caroline Mala Corbin, professor of law at the University of Miami. “The right to abortion doesn’t vanish, it just is up to the states.”

Every major U.S. Supreme Court abortion decision in the past 40 years has come down to a 5-4 vote. Because Kennedy often acted as the swing vote in favor of preserving legal abortion, legal experts agree that a more conservative court would likely rule against abortion when a relevant case reaches the bench.

Even with Roe v. Wade intact, states have heavily restricted when and where someone can terminate a pregnancy. And if that federal protection were to disappear, 23 states would be at risk of losing the right to an abortion completely, according to the Center for Reproductive Rights.

“In a lot of ways, Roe has been hanging by a thread for at least 20 years,” said Jennifer Lawless, director of the Women and Politics Institute and a professor of government at American University. “It’s almost a foregone conclusion that as soon as the court has the opportunity they’ll overturn Roe, and the decision will go back to the states.”

Four states are already prepared to outlaw abortion the minute Roe falls. Legislators in Louisiana, Mississippi, North Dakota, and South Dakota have passed trigger laws that would effectively ban abortion without any further legislative action. Legal experts told Rewire.News that more states eager to ban abortion will likely start taking action following Kennedy’s departure.

Thirteen states have pre-Roe bans on the books that could be reinstated (Louisiana has both a trigger law and a pre-Roe ban). In states where these bans were never deemed unconstitutional, they could immediately spring into effect. But in states where a court previously blocked the ban, legislators must petition to have that decision overruled.

Pro-choice advocates want to see those pre-Roe bans removed, but some Democratic lawmakers’ efforts have been unsuccessful. A bill in Rhode Island aiming to codify abortion rights into state law has twice failed to reach a vote. However, Kennedy’s retirement has reignited the state legislature’s debate, the Providence Journal reports.

Meanwhile, eight states have laws that explicitly protect the right to legal abortion, according to the Guttmacher Institute, and states such as New York have stalled on similar laws.

If pro-choice advocates don’t prepare for the absence of Roe at the state level by passing more laws guaranteeing the right to abortion and wiping out conservative majorities in state legislatures, said Gloria Totten, president of the Public Leadership Institute, “we will be missing a really key part of what needs to happen.”

Because state legislatures hold so much power, thinking about reproductive rights when voting in November “takes on new meaning and new significance,” Lawless said. “It’s possible that state legislative candidates would be successful highlighting that the stakes have changed and there’s now a high likely that there won’t be some broad federal protection.”

The record number of women running for office this year—the majority of whom are Democrats—has the potential to change the political landscape across the country, which could, in turn, change the landscape of abortion laws. Even though states could eventually determine the legal status of abortion within their own borders, a so-called “blue wave” would increase the likelihood that more states would protect the right to abortion.

Kelly Baden, director of reproductive rights for the State Innovation Exchange, believes there will be opportunities to guarantee abortion remains legal in more states before the downfall of Roe.

“I am optimistic that there will be enough of a public outcry and enough of a new crop of legislators with the political will to take this issue on,” Baden said.