A group of Catholic nuns and lay people is calling on the Pope to officially get rid of the "Doctrine of Discovery," a group of 15th century decrees that were the basis for European explorers' claims over aboriginal land.

The doctrine even gave Europeans the right to kill or enslave people who refused to convert to Christianity.

Sister Maureen Fiedler, an American nun and a blogger for the National Catholic Reporter, is a member of the Loretto community that is lobbying to revoke the doctrine.

"I think that we're speaking on an issue that's really central to questions of justice and peace in the world and I can't image Pope Francis wouldn't resonate with this because so much of his own message has to do with justice and people that are downtrodden and creating peace," she said.

"I can't imagine he wouldn't repudiate this if he just had the time to think about it for a few minutes."

Fiedler says the Doctrine of Discovery has been cited in U.S. Supreme Court cases as recently as 2005 on regulations for American Indian land. The United Nations' Permanent Forum on Indigenous Issues has called it "racist," "morally condemnable" and "socially unjust."

There has been no response yet from the Vatican.