The Case: Dobbs V Jackson Women's Health Organization.

The name gives little clue as to the controversial nature of the case that is to be decided by the US Supreme Court.

For it is about abortion, and the law governing its provision in the US, which has become one of the most controversial topics in American politics.

A big indicator of just how controversial it is was the leaking of a draft judgment in the Dobbs case last month. Nobody can remember a similar incident. The workings of the US Supreme Court are confidential. Judgments and other working papers simply do not leak. Except in this case, where America's law on abortion is at stake.

The issue before the court is whether it is lawful for the state of Mississippi to seek to ban abortions being carried out beyond the 15th week of pregnancy. A law passed by that state was challenged on the grounds that it contravened the US constitution as interpreted in a case called Roe v Wade.

The leaked draft ruling argues that the ruling in Roe v Wade was wrong, and that the power to regulate abortion should be returned to the individual states.

In the leaked draft, Justice Samuel Alito wrote: "At the time of Roe, 30 states still prohibited abortion at all stages. In the years prior to that decision, about a third of the states had liberalised their laws, but Roe abruptly ended that political process. It imposed the same highly restrictive regime on the entire nation, and it effectively struck down the abortion laws of every single state.

"As Justice Byron White aptly put it in his dissent, the decision of the court represented the 'exercise of raw judicial power', and it sparked a national controversy that has embittered our political culture for a half-century."

Mr Justice Samuel Alito

Much of the controversy around Roe v Wade stems from the fact that the national abortion law in the US was set by judges, not by elected politicians at either state or federal level. And those judges relied on the concept of implied or unsaid constitutional rights.

That is rights that are not written down in the constitution, but which the judges say are implied by other written parts of the constitution, along with legal precedent, history, custom and tradition in US society.

The ruling was tested again by the Supreme Court almost 20 years later, in a case known as Casey, in which the central issue of preventing states from regulating abortion was upheld on the basis of implied Constitutional rights.

The leaked draft ruling, however, contends that the reasoning used by the court in both Roe and Casey was wrong, and should be overruled in the Dobbs case.

Justice Alito, in the leaked draft, wrote: "The constitution makes no reference to abortion, and no such right is implicitly protected by any constitutional provision, including the one on which the defenders of Roe and Casey now chiefly rely - the Due Process Clause of the Fourteenth Amendment.

"That provision has been held to guarantee some rights that are not mentioned in the constitution, but any such right must be 'deeply rooted in this nation's history and tradition' and 'implicit in the concept of ordered liberty'. The right to abortion does not fall within this category."

"Roe was egregiously wrong from the start" - Alito

It is unusual for a Supreme Court to overturn the rulings of a previous court, but it is not impossible.

Usually superior courts rely heavily on a concept known as Stare Decisis - a legal principle that discourages overturning precedents, or previously decided cases, unless certain conditions are met.

In this case, the leaked draft suggests Justice Alito (and the other judges who apparently support his view) believe the precedent rule does not apply.

He wrote (in the leaked draft): "Stare Decisis, the doctrine on which Casey's controlling Opinion of the Court opinion was based, does not compel unending adherence to Roe's abuse of judicial authority.

"Roe was egregiously wrong from the start. Its reasoning was exceptionally weak, and the decision has had damaging consequences. And far from bringing about a national settlement of the abortion issue, Roe and Casey have inflamed debate and deepened division. It is time to heed the Constitution and return the issue of abortion to the people's elected representatives".

What could happen if Roe and Casey are over-ruled in the Dobbs case?

There is likely to be a rapid reversion to the situation before 1973 - that is to say, a patchwork of regulations across the 20 states - abortion would be legal in some states, illegal in others.

Twenty-six states sought a Supreme Court decision in the Dobbs case, arguing that the right to regulate abortion law lies with the states. That, they say, would entitle a state like Mississippi to bring in a law banning abortion beyond 15 weeks of pregnancy, instead of adhering to the second-trimester rule introduced by the Roe ruling.

Other states have already gone further in anticipation of the court striking down Roe v Wade. Some 13 states have so-called "trigger laws" - laws already enacted, but which would only come into effect in the event of a Supreme Court ruling overturning Roe v Wade. Most of these would see a total ban on abortion in those states, starting 30 days after a ruling of the Supreme Court.

Another dozen or so states are expected to bring in their own laws, restricting or banning entirely abortion, if the Supreme Court rules they have the power to do so.

But the other half of America’s states either have local laws allowing abortion, or are likely to move towards legalising abortion at state level. In some states, such as Michigan, which has pre-Roe v Wade laws on the books criminalising abortion, state attorneys general have said they will not prosecute any woman obtaining an abortion or any doctor performing one.

The draft ruling also does not prevent the federal parliament, the United States Congress, from passing federal level legislation, making abortion legal in all states. However, a bill to do just that failed in the Senate by 49 votes to 51 last month.

There is also a possibility that the US constitution could be amended to include a specific right to abortion. However, this is a tricky process (and not just because the issue is very controversial, particularly in those states seeking to criminalise abortion).

The process itself is difficult: unlike in Ireland a national referendum is not the route to constitutional change, so a direct vote is not possible. Instead, a proposal to change the US constitution begins with a motion backed by a two thirds majority (a "qualified majority vote") in both houses of the US Congress. Or a resolution by a Constitutional Convention called by two thirds of the States of the Union.

Any resulting motion to amend the constitution must then be ratified, which requires the support (under their own laws) of three quarters of the state legislatures, or two thirds of conventions called in each state to ratify or not ratify the amendment. (Amending EU treaties requires the support of every member state).

The issue of who has the power to regulate on topics - the states or the federal government - is a perennial one in the US, and indeed in all federal and quasi-federal systems, such as the European Union, where each new treaty usually involves an argument about where the "competence" to act lies - with the member states or the EU institutions in Brussels.

One of the chief discussion points in the Lisbon Treaty debates was around the extent to which it would be an explicit list of - or delimitation of - the powers of the EU; unless it was written down as an EU power, everything was deemed to be a power of the member states. As abortion is not an EU competence, member states, such as Poland and Ireland, could move in radically different directions when it came to regulating abortion.

But things don't stay the same. If Roe v Wade is overturned, it will not simply be a case of returning to the status quo ante of almost half a century ago.

Fresh battle ahead over data privacy

One particular area that may lead to a clash of laws is the regulation of so-called abortion pills. Most abortions in the US are now carried out by abortion pills, not surgical procedures. Such chemical alternatives were not available at the time of Roe v Wade.

During the Covid pandemic suppliers in US were permitted to mail out abortion pills to women. This temporary derogation has now been made permanent. It seems some states will move to ban abortion pills, but there are questions to be resolved about the legality of banning the mailing of abortion pills from other states where they are legal.

Another area that has developed since the early 1970s has been IVF treatment to help couples have children. The process involves fertilising eggs and implanting one or more into the womb to begin pregnancy.

Questions are now being asked in the US about proposed or trigger laws that would outlaw abortion from the moment of conception.

Some state laws appear to exempt IVF - and in particular the process of disposal of unused embryos - from the criminal law, but there is ambiguity when it comes to "selective reduction", when a woman whose treatment results in multiple pregnancies, and who has one or more of these foetuses terminated to protect the viability of other foetuses or the life of the mother.

IVF has been largely shielded from regulation under the Roe ruling, but this could change if it is overturned.

And in the Age of the App, where the word "cookie" has developed an entirely new meaning in the decades since Roe v Wade, a new issue to be grappled with is the data privacy aspects of any new abortion laws.

On Tuesday, US Vice President Kamala Harris met a group of data privacy experts to discuss the possibility that states which have "criminalised abortion could subpoena a woman's personal data [...] including, for example, the vulnerability of women who are using menstrual tracking apps, those who use a search engine to find certain locations or certain health information in terms of their reproductive health, and how vulnerable those searches will be to bad actors attempting to track their history".

If Roe v Wade is overruled, the issue of data privacy in the US, which lacks an equivalent of Europe’s GDPR, is sure to become a new, and highly charged, battle ground in the US's culture wars.