The Missouri policy is being pushed by a Republican state Rep. Mary Elizabeth Coleman, who said that it specifically targets a clinic in Illinois just across the river from St. Louis that opened in 2019.

If you believe that every person deserves dignity and respect and protection, then you want to protect your citizens, no matter where they are.

Her effort puts Missouri at the forefront of a new round of action in state capitals where conservatives are rushing to pass legislation ahead of an anticipated Supreme Court ruling.

The Missouri proposal can be voted on at any time before the session ends in May. The legislation goes further than most abortion restrictions across the country and attempts to evade legal challenges by adopting the same private enforcement mechanism as Texas, which the Supreme Court has allowed to stay in place for the last six months. If the suit is successful, the judge can award at least $10,000 in damages.

Legal scholars say the Missouri proposal could force courts to contend with questions that date to the Fugitive Slave Act two centuries ago.

There is no clear precedent saying that states can regulate out-of-state conduct if it affects one of their citizens.

As a growing number of people seek abortions outside their home states and as abortion-rights groups raise money to help low-income patients pay for travel and lodging, Missouri is moving. If the Supreme Court upholds a Mississippi law prohibiting abortion at 15 weeks, that trend is expected to surge. Up to half of the states are expected to limit or ban abortion immediately if that happens.

If the Missouri amendment becomes law, other states are likely to explore their own version.

The director of the anti-abortion group Human Coalition Action in Texas is working with the same lawmakers who drafted the state's six-week ban on abortions.

She said that they have had the benefit of seeing what an almost abortion-free state could look like. The Missouri model would close those loopholes.

According to James Bopp Jr., the general counsel for National Right to Life, there is some legal precedent for such policies: several federal and state laws already prohibit the transportation of minor children across state lines for an abortion without parental consent. He noted that Missouri's attempt to extend that to adults is completely novel.

The most popular method of abortion in the U.S. is abortion pills.

Texas is one of several states that have moved to crack down on the practice of sending drugs by mail. Many others are looking to implement similar bans in the wake of the Biden administration's move earlier this year to loosen restrictions on the pills. Coleman's proposal in Missouri also includes a prohibition.

The anti-abortion-rights activists and elected officials who favor the policies argue that they can eliminate all abortions without discouraging travel across state lines, and that they are responding to progressive advocates who are raising money to help people get abortions in other states.

The Students for Life of America lobbies for restrictions in all 50 states and has chapters that help people circumvent pro-life laws.

Andrew Beck is a senior staff attorney with the American Civil Liberties Union's Reproductive Freedom Project.

He said that it encourages people to spy on and rat out their friends and family.

Legislators in Democrat-controlled states have drafted measures to protect in-state physicians who provide abortions and those who help people cross state lines, as a result of the conservative effort. Coleman's proposal doesn't allow the patient to be sued, but these measures give legal protections to the pregnant person.

The first committee of the California Legislature passed a bill on Tuesday that would protect Californians from the kind of civil lawsuits contemplated by Missouri.

We don't believe that any other state should have the ability to reach into our state and control the actions of our citizens or doctors.

A bill in Washington state is waiting for the governor's signature. Legislators in Oregon just approved a budget that will cover abortion fees, travel and lodging expenses for state residents and travelers alike, and expand the number of abortion providers in the state.

Many expect a wave of patients from Idaho, which this week became the first state to pass a ban on abortion after 6 weeks of pregnancy.

The right to interstate travel is protected by the Constitution, and the Biden administration should give guidance on that, as well as strengthen the protections of the Health Insurance Portability and Accountability Act.

If more states follow Missouri's lead, abortion-rights supporters stress that even these kinds of state and federal protections would only be a partial solution.

Beck said that not everyone can fly to California or travel across state lines.