FOR more than a century the government of Canada ran a system of residential schools for indigenous children, taking them from their parents—by force if need be—and putting them into institutions where many were physically and sexually abused. Seven years ago Stephen Harper, then Conservative prime minister, apologised on the government’s behalf to the 150,000 children and their families for the brutal attempt to wipe out their cultures. On December 15th Justin Trudeau, the new Liberal prime minister, apologised again, saying the “abhorrent” system represented “one of the darkest chapters in Canadian history”. He then said he would ask Pope Francis to apologise too. Why involve the pontiff? Although this was a government programme, between 1883 and 1996 churches ran the 139 residential schools. Priests and nuns of the Roman Catholic church controlled the majority of them. Yet alone among the churches involved, its national body in Canada has refused to apologise on grounds that a decentralised structure leaves this duty to individual dioceses. Some have. But Catholic foot-dragging over payment of their agreed share of the $1.4 billion settlement of a class-action lawsuit by former students prompted the federal government to take the dioceses to court. This would seem egregious enough to merit a papal pronouncement; Mr Trudeau is speaking up now because of a promise he made during the recent election campaign to implement all 94 recommendations of the truth-and-reconciliation commission set up as part of the settlement agreement. Its final report was delivered on December 15th.

The prime minister may have some luck getting papal action on recommendation “58”, which calls on Pope Francis to visit Canada and apologise to former students, their families and communities “for the Roman Catholic Church’s role in the spiritual, cultural, emotional, physical, and sexual abuse of First Nations, Inuit, and Métis children in Catholic-run residential schools”. Pope Francis seems open to acknowledging the church’s past sins. He has apologised to the victims of sexual abuse by Catholic priests in Ireland and asked forgiveness during a trip to Bolivia last July for the church’s role in the sins of colonialism. Where Mr Trudeau will run into greater difficulty is implementing recommendation “45”. It calls for a new royal proclamation (Canada is a constitutional monarchy) that among other things would repudiate two concepts based on papal bulls from the 15th century: the Doctrine of Discovery and terra nullius.

This is much trickier ground. The 15th-century bulls that are collectively known as the Doctrine of Discovery gave European explorers carte blanche “to invade, capture, vanquish, and subdue all Saracens, pagans, and other enemies of Christ, to put them into perpetual slavery, and to take away all their possessions and property”. Terra nullius is the convenient fiction that if no Europeans were present, the land was uninhabited. Both concepts crept into national and international law and underlie the legal existence of English-speaking settler states such as Canada, the US and Australia. Some indigenous groups have long called for the Vatican to repudiate the offending bulls. Some theologians suggest this might have been done in 1537, though the proof is hazy. Those advocating a repudiation say the doctrine is still very much alive. A group of Canadian and American native chiefs are planning to march to Rome from Paris in May to petition the pope in person. It is unclear what the legal impact would be if either the pope or Mr Trudeau publicly repudiated the concepts. Neither seems likely. The pope’s speech in Bolivia provided a perfect opportunity to do so if he was so inclined. He will have another chance if he accepts the invitation of the Quebec government to visit the French-speaking province in 2017 on the 375th anniversary of the founding of Montreal. (The prime minister’s office has yet to issue an invite.) But the last word from the Vatican is that a trip to Canada is not currently contemplated.