An unprecedented leak of a draft supreme court decision shows a majority of justices support ending federal protections for abortions in arguably the most controversial court case in generations.

While the draft could still change, if it is not substantially altered it would result in 26 states immediately or as soon as practicable banning abortion, a sea change in the American legal and political landscape.

Why would half of the US outlaw abortion?

If the draft decision remains substantially unchanged, it would return the issue of abortion to the states, 26 states stand poised to ban or greatly restrict it. Until the court issues a final decision, the right to abortion is protected under federal law.

That right was established in the landmark 1973 case Roe v Wade. Roe found pregnant people have a constitutional right to terminate a pregnancy up to the point a fetus can survive outside the womb, roughly considered 24 weeks gestation, and a legal principle called “viability”.

The court’s finding in Roe invalidated dozens of state abortion bans, and made it illegal for states to outlaw abortion before viability. The case that was the subject of the leak on Monday, called Dobbs v Jackson Women’s Health Organization, considered a Mississippi law that banned abortion at 15 weeks. Even though this is not a total ban, it strikes at the heart of the holding that established a federal right to abortion.

Do Americans support abortion?

A recent poll found 70% of Americans think abortion is a choice that should be left to a woman and her doctor, and polling over time has shown support for legal abortion has changed little since Roe v Wade was decided. Only a small minority think abortion should be completely illegal.

If most Americans support the right to abortion, can Congress intervene?

The federal right to abortion hangs on a supreme court decision because, in the nearly 50 years since Roe v Wade was decided, congressional leaders failed to protect the right in statute.

While there are Democrat-led efforts to protect abortion, they are stalled in the Senate. That’s because any new statute would need 60 votes to pass, and the 100-member Senate is evenly split. Democrats broadly support abortion rights, while Republicans almost universally oppose efforts to protect abortion rights.

Some Democrats have proposed ending the 60-vote rule, called the filibuster, to move legislation on abortion and other key items on Joe Biden agenda’s forward. The president has endorsed such a change.

However, two key Democratic senators, Joe Manchin and Kyrsten Sinema, oppose such a change. It is unclear how the leaked opinion may change their position. Sinema has said she supports abortion rights, while Manchin has issued conflicting messages.

Biden has called on Americans to elect more members of Congress who support reproductive rights in the upcoming midterm elections in November.

How soon would abortion become illegal?

If the issue of abortion were to return to the states, 26 would immediately or as soon as practicable ban abortion.

States would do so through a mix of abortion bans that were invalidated by Roe v Wade but remained on the books, abortion bans “triggered” if Roe is overturned, and laws that limit the gestational age at which a person can terminate a pregnancy. All will probably be the subject of court challenges.

For example, an abortion ban enacted in 1931 could go back into effect in Michigan. There, the Republican-led legislature supports the ban, but the state’s Democratic governor is challenging it in state court.

In Arkansas, the state legislature has enacted a “trigger” ban. There, the state attorney general would need to certify the central holding of Roe was indeed struck down. The attorney general, a Republican, would likely seek to do so quickly.

Trigger bans vary from state to state. While Arkansas requires an attorney general certification, Wyoming requires the governor to certify Roe has been overturned before the law goes into effect five days later.

Other bans, once blocked by the courts because of Roe, could also go into effect. Enforcement of a six-week abortion ban in Iowa could go into effect. Because that is just two weeks after a pregnant person might miss a period, and before most people know they are pregnant, it is effectively a near-total ban.

In all cases, laws will probably be challenged by reproductive rights groups, and it will take time for cases to move through state and perhaps federal courts. Some experts have estimated it could take between six months to two years for most cases to be settled.

What is certain is in that time, Republican-led states would probably seek to push the envelope in terms of criminalizing abortion, and seek to enforce the bans they already have on the books.

How will people terminate pregnancies in states where it is banned?

Making abortion illegal will not stop abortions. People who live in states where abortion is outlawed but want to terminate a pregnancy may seek to travel to states where it remains legal, or obtain medication to end a pregnancy.

Medication abortion can safely end pregnancies up to 10 weeks gestation using a two-pill protocol. However, in states where abortion is illegal, those pills would need to be obtained illicitly, perhaps through through the mail.

Patients who want to go to clinics, or whose pregnancy is too far along to be self-managed with medication, would need to travel potentially hundreds of miles to states where abortion is legal. That may be an impossible hurdle for women whose finances are strained or who cannot find childcare.

People who live in states where abortion remains legal would also be impacted, because they would face longer wait times for appointments as patients flood into clinics from out-of-state. This could create a secondary wave of travel.

Even more broadly, outlawing abortion would substantially undermine care for basic obstetric procedures, such as miscarriage and ectopic pregnancies, in a country which already has among the highest maternal mortality rates in the developed world.

Nearly half (44%) of all future obstetricians and gynecologists are trained in states that would outlaw abortion, making it impossible to train all new doctors in the skills needed to manage induced or spontaneous abortion. Even more doctors may be frightened to provide evidence-based care to women who face life-threatening complications, if their condition is not imminently emergent – but may become so.

How are liberal states responding?

Some Democrat-led states, such as Oregon, are working to protect abortion by providing funds for people who travel to their states to obtain abortions. Others, such as California, are working to build capacity for the thousands of woman who could suddenly find the nearest abortion clinic there.

But in all cases, these efforts will be incomplete. Not all people will be able to travel or obtain medication abortions, and may forced to carry an unwanted pregnancy to term.