‘How unusual is it,’ I was asked on BBC Radio Ulster, ‘for the Supreme Court to say it has no jurisdiction to decide a case but then to say what it would have decided if it could?’

Just a couple of hours after the UK’s highest court had delivered a 143-page judgment on abortion law in Northern Ireland, my interlocutor had come up with a particularly astute question.

Thinking quickly, I told him this was not uncommon in the lower courts. A judge might say how a case would have been decided on a different view of the law, just in case an appeal court found that the judge’s legal analysis had been wrong. But why would four Supreme Court justices deliver judgments that were not only obiter but moot? They could only have been trying to put political pressure on legislators.

Seven justices were ruling on a claim brought by the Northern Ireland Human Rights Commission, a statutory body set up after the 1998 Good Friday Agreement. The commission was challenging provisions in the Offences Against the Person Act 1861 that make it illegal to procure an abortion; provisions that were modified in the rest of the United Kingdom by the Abortion Act 1967. In Northern Ireland, though, termination of pregnancy is punishable with life imprisonment unless done ‘for the purpose of preserving the life of the mother’.

Because the 1861 act is primary legislation, the Supreme Court cannot overturn it. Instead, the commission wanted the court to declare the legislation incompatible with the right to respect for private and family life guaranteed by article 8 of the human rights convention.

The court was shown harrowing statements from women from Northern Ireland whose babies had failed to develop properly and would inevitably be stillborn. In other cases, women had become pregnant through rape. A child under the age of 13 was carrying a baby as a result of sexual abuse by a member of her family. None of them could have abortions in Northern Ireland.

Instead of helping one of these women to bring a claim, the commission decided to bring proceedings in its own name. Courts in Northern Ireland decided it had the power to do so. The commission said it would have been difficult to find a claimant who was seeking an abortion for one of the specified reasons at the precise time proceedings were commenced.

But four of the seven Supreme Court justices held that the commission had no power to argue that primary legislation was incompatible with human rights. The commission had not identified any unlawful act or any actual or potential victim. This was not merely a question of statutory construction: Lord Mance, (pictured) for the majority on this point, thought it implausible that parliament had intended to give the commission carte blanche to challenge any UK primary legislation of its choosing.

Surely the whole point of the commission is to challenge legislation that violates human rights? The minority judges thought it would be anomalous to treat the Northern Ireland commission differently from its counterparts in Great Britain. You can imagine the fights that must have been going on behind the justices’ closed doors: Mance and his colleagues Lord Reed, Lady Black and Lord Lloyd-Jones were accused of rejecting an interpretation that ‘gives effect to the ascertainable will of parliament’ and preferring a ‘literal construction which will frustrate the legislation’s true purpose’.

Cynics sometimes accuse judges of reaching a decision on the merits and then contriving the law to produce the desired result. But that was not the case here. Far from supporting the current law in Northern Ireland, Mance was satisfied it was ‘untenable and intrinsically disproportionate in excluding from any possibility of abortion pregnancies involving fatal foetal abnormality or due to rape or incest’. That opinion was shared by Lady Hale, Lord Kerr and Lord Wilson, making it the majority view.

But should they have said so, given that they had no jurisdiction? Mance’s answer was that the law clearly needed radical reconsideration and it was inevitable that a challenge brought in the name of a victim would result in a declaration of incompatibility.

Hale went further. Compatibility was not a matter on which a democratic legislature enjoyed unique competence. ‘In some ways, the courts may be thought to be better qualified because they are able to weigh the evidence… in a dispassionate manner.’

But Reed, the new deputy president, endorsed the point I made earlier: having found that the commission had no standing, ‘it would ordinarily follow that the court should express no view’ on compatibility. He thought the court should steer clear of politics, leaving these issues to be debated in ‘democratically accountable institutions’.

Whether those institutions will follow the court’s non-binding steer remains to be seen.