The British government’s Legacy and Reconciliation Bill, passed in September, stops most prosecutions for alleged killings by armed groups and British soldiers during “the Troubles” – the period in Northern Ireland from the 1960s to the 1990s during more than 3,500 people died.

The law has been widely opposed by people in Northern Ireland, as critics say it shuts down access to justice for victims and survivors.

Ruling on Wednesday in a legal challenge brought by victims and their families, Justice Adrian Colton said the law’s provision for conditional immunity from prosecution breaches the European Convention on Human Rights.

The judge also said the law will not contribute to peace in Northern Ireland.

“There is no evidence that the granting of immunity under the act will in any way contribute to reconciliation in Northern Ireland; indeed the evidence is to the contrary,” he said at Belfast High Court.

However, Colton ruled that a new body set up to probe Troubles killings, to be loosely modeled on South Africa’s post-apartheid Truth and Reconciliation Commission, could carry out human rights-compliant investigations.

The United Kindom’s government said it will consider the ruling carefully but added that it remained “committed” to implementing the legacy bill.

Northern Ireland was the only part of Ireland to remain in the UK after the partition of the island in 1921. However, Catholics – who were once a minority but now form the majority of the population of Northern Ireland – generally wished to join the Republic of Ireland, whereas Protestants predominantly wished to remain in the UK.

That divide eventually lead to the Troubles, and to sectarian divisions that splintered towns and cities, and continue – in less entrenched forms – to this day.

‘Big questions’ for the UK government

Amnesty International said there were “significant questions” for the UK’s government to answer, and urged officials to repeal the law.

“The core part of this legislation was the immunity from prosecution. That has now been stripped out, struck out from the law. So it’s back to Parliament and back to the UK government about what they are going to do next,” said Grainne Teggart of Amnesty.

“There are big questions for the secretary of state for Northern Ireland to answer how he plans to proceed,” Teggart told Al Jazeera. “As Amnesty, we would urge him to now go back to the drawing board, to think again, to repeal this legislation and replace it with something that actually prioritises and respects victims’ rights.”

Al Jazeera’s Harry Fawcett, reporting from Belfast, said there is potentially further action in the court.

“There is another action being brought in Europe by the Irish government as well, so this is not over yet,” Fawcett said.

“The judge did endorse that view, that by not addressing the claims for justice by victims, that itself could inhibit reconciliation going forward.”

In December, the government of the Republic of Ireland launched a separate legal case against the UK government over the Troubles law at the European Court of Human Rights.

The 1998 Good Friday peace accord largely ended violence in Northern Ireland, and British authorities say the law will allow the country to move on.

But those who lost loved ones have said the law would airbrush the past and allow killers to get away with murder. Dozens of legacy inquests have yet to be heard.

Martina Dillon, who was among those who brought the case, said she will “fight until I get truth and justice”. Her husband, Seamus, was shot dead in 1997.

Ongoing lawsuits include a case brought against Gerry Adams – the former leader of the nationalist political party Sinn Fein, which seeks the reunification of Northern Ireland and the Republic of Ireland – by three people who were wounded in bombings attributed to the Irish Republican Army more than 50 years ago.

The case is likely to be one of the last court efforts by victims seeking justice.