A long-running legal battle heads to the Supreme Court on Monday as two B.C. residents accused of arranging the honour-killing of a young relative in India continue to fight the federal government's efforts to extradite them.

Jaswinder (Jassi) Sidhu was found dead in a canal in India in 2000.

India has been trying for years to extradite Malkit Sidhu and Surjit Badesha, both of Maple Ridge, B.C., to face trial.

They are the mother and uncle of Sidhu, a B.C. woman whose body was dumped after her throat was slashed in Punjab. Her young husband, Sukhwinder (Mithu) Sidhu, was badly beaten and left for dead.

She was allegedly targeted for secretly marrying the rickshaw driver, a man of much lower social status, instead of the older man her family had arranged for her to wed in Canada.

Sidhu and Badesha were arrested in Canada in 2012, suspected of orchestrating the so-called "honour killing."

Indian courts asked to have the pair extradited to face trial, but a surrender order signed by former Justice Minister Peter MacKay was challenged and ultimately struck down by a B.C. appeals court last year.

The ruling said the pair could be subject to violence, torture or neglect based on India's human rights record.

Badesha's lawyer Michael Klein says the pair could be in danger if sent to India, and Canada is obliged to protect them.

The Supreme Court of Canada will hear an extradition case Monday related to the 2000 death of Jassi Sidhu.

"Both of these people are elderly and both have health issues and that makes them more vulnerable in an Indian prison system, especially one which has been characterized as quite brutal," he told CBC News.

But in a 46-page submission to the court, the attorney general of Canada said the B.C. appeal court "erred" and called its decision an "unwarranted interference" with the minister's order to return alleged perpetrators in the "brutal and notorious 'honour' killing of a Canadian citizen." It said the ruling jeopardized Canada's ability to live up to its obligations to extradition treaty partners.

"The need to fulfil Canada's obligations in relation to extradition is always a crucial factor precisely because of the objectives of the extradition regime including the importance of seeing justice done in the jurisdiction in which crimes are committed and the need to prevent Canada from becoming a safe haven for criminals," it reads.

Canada has received diplomatic assurances the two won't be executed, tortured or mistreated in India and that they will have access to Canadian officials.

But human rights lawyer Adriel Weaver says that's not enough.

"The prohibition on torture is absolute, and diplomatic assurances are inherently ineffective and unreliable," she said.

Human rights and justice

A number of human rights groups have intervened in the case, including Canadian Lawyers for International Human Rights, Canadian Centre for Victims of Torture, Canadian Council for Refugees, David Asper Centre for Constitutional Rights Intervener Active and the South Asia Legal Clinic of Ontario.

Juda Strawczynski, president of Canadian Lawyers for International Human Rights, said alternatives to extradition are available in cases when Canada isn't satisfied with a recipient country's human rights record is spotty, including a trial in absentia or prosecution in Canada.

But he said Canada cannot forego human rights in the pursuit of justice.

"We have to look at what we can fully consider as justice, and here we have to be mindful of Canada's reputation and trying to avoid injustices as much as possible," he said.

Seven men were convicted of the crime in India, but several of those convictions have been overturned on appeal.