Native American leaders want to ask Pope Francis during his visit to the U.S. to renounce a more than 500-year-old doctrine that allowed for European explorers to subjugate Native Americans when they began colonizing America, according to Catholic Online. Various Native American tribal leaders are planning a protest next month while the Pope is in Philadelphia to appeal to him to repeal a 1452 “Doctrine of Discovery” signed by Pope Nicholas V authorizing European explorers to conquer infidel territory and declare war on all non-Christians, according to the Anti-Defamation League. The doctrine, in place 40 years before Christopher Columbus landed in the Western Hemisphere, has never officially been renounced by the Roman Catholic Church.

The doctrine also called for the enslavement of any Native Americans explorers might find. Though other popes throughout the 16th and 17 centuries condemned the idea that Native Americans should be treated as “animals” and even at one point excommunicated any Catholic who held Native American slaves, the doctrine remains in place. 

The doctrine is a very old, deep wound for Native Americans that is still relevant in today’s society, Oren Lyons, a Native American "faithkeeper" and activist, told Catholic Online.

During a July visit to Bolivia, Francis apologized to and asked forgiveness from Native Americans for “grave sins” committed by the Catholic Church when the Americas were being colonized, according to the Independent. Although many Popes have preached against violence, the church has never apologized directly to Native Americans, Francis said. Native American leaders were pleased with the apology, but still want more.

Some 2 million people are planning to attend the Pope’s Philadelphia visit, and about 9,000 people have signed on as volunteers for the event, the Harrisburg (Pa.) Patriot-News reported.

The pope, who plans to be in Philadelphia from Sept. 25 to 27, is also scheduled to stop in Washington, D.C., and New York City during his trip to the U.S.