A log cabin is seen on the Pine Ridge Reservation in southwest South Dakota on Feb. 28, 1956. (AP)
Melissa J. Gismondi is a historian and journalist. She holds a Ph.D. in North American history from the University of Virginia.

In 2016, the General Assembly of the Presbyterian Church (PCUSA) repudiated the historic “doctrine of discovery.” Although it might sound benign, the doctrine was the pernicious theory that Christians could claim and conquer land inhabited by non-Christians. It helped justify and promote the violent colonization of indigenous lands throughout the Americas.

This summer, the Assembly followed up on that repudiation by issuing a report outlining specific actions the church can take to grapple with the doctrine’s legacy. They include official acknowledgments before meetings of the indigenous nations on whose land the meeting is taking place, as well as more discussion of indigenous theologies and educational resources on the doctrine.

PCUSA is just one of several mainline Protestant churches to repudiate the doctrine and evaluate their participation in one of America's founding sins. In 2012, for instance, the United Methodist Church followed its repudiation with a study outlining the participation of prominent Methodists in the 1864 slaughter of more than 150 peaceful Arapaho and Cheyenne people during the Sand Creek Massacre.

Such actions raise awareness among congregants about the role their faith and faith community has played in American colonialism at home, not just abroad. They also have the power to change the future. Because the colonization of Native American land isn’t an event; it’s a process. It’s ongoing and reinforced every day by the decisions millions of Americans make. That’s why it matters that churches — which provide the moral compass for millions of people — are raising this issue now. And it matters what happens next.

Most Americans aren’t familiar with the doctrine of discovery, but it’s one of the most important ideas in history. It traces back to a series of papal bulls — public decrees — issued in the 15th century. Pope Nicholas V issued the first one in 1452. It was followed by “Romanus Pontifex” in 1455 and Pope Alexander VI’s “Inter Caetera” in 1493, the year after Christopher Columbus started his famous voyage to the so-called New World.

Three years later, King Henry VII issued a similar edict to John Cabot, who explored the North American coastline. By basing land ownership on Christian discovery, the doctrine tried to negate indigenous peoples' right to the lands they lived on.

In addition to the seizure of indigenous land, Alexander VI’s edict called upon the seizure of indigenous souls, too. “Inter Caetera” declared that once Christians had conquered new territory, they had to bring “barbarous nations” to the faith. Believing themselves to be doing God’s work, Catholic, and later Protestant, missionaries spread throughout the Americas, trying to destroy diverse aspects of indigenous culture.

After independence, American lawmakers carried the doctrine of discovery into the 19th century, when they continued using it to extinguish indigenous land claims. In 1823, the Supreme Court heard the first of three cases that would determine Native American law for years to come. Johnson v. M’Intosh concerned competing claims over land in southern Illinois and Indiana. Thomas Johnson had obtained the land in the 1770s by purchasing it from people in the Illinois and Piankeshaw nations. After independence, however, the sellers sold the same tract to the federal government, which then sold it to William M’Intosh.

Johnson protested M’Intosh’s claims to the land, but a unanimous court sided with the defendant, citing the doctrine of discovery. Chief Justice John Marshall argued that because European nations had determined ownership to be based on Christian discovery, the Illinois and Piankeshaw peoples had no right to own the land, let alone sell it to a private buyer. As successors of the British, federal and state governments in the United States were the original owners of the land, Marshall maintained. It was theirs for the taking — and selling.

The doctrine of discovery informed subsequent cases on land ownership and indigenous sovereignty, such as Cherokee Nation v. Georgia. In this 1831 case, Marshall, again writing for the court, ruled indigenous nations were “wards” of state and federal governments. They couldn’t own land independent of what the government had granted them, and they couldn’t protest the passage of state or federal laws within their boundaries.

Such justifications proved expedient to President Andrew Jackson, who campaigned in 1828 on a policy of “removing” eastern Native nations to reservations west of the Mississippi River. Although the Supreme Court held in Worcester v. Georgia in 1832 that the Cherokee nation did, in fact, hold sovereign powers, Jackson refused to enforce the decision.

A lawyer by trade, the president understood that the doctrine of discovery — and the legal arguments stemming from it — ran deep in American society. It confirmed his belief, which his pious wife, Rachel, promoted, that white American Christians had a right to create settlements on indigenous lands. As a land speculator, these settlements also helped line his pockets. As a result, Jackson violated Cherokee sovereignty by implementing their forced removal in the 1838 Trail of Tears relocation, during which some 4,000 died.

And this doctrine and the jurisprudential canon that stemmed from it continued to shape American law well into the 20th and even 21st centuries. In 1955, Justice Stanley Reed used Johnson v. M’Intosh to justify dismissing claims made by the Tee-Hit-Ton Indians.

The Supreme Court even referred to the doctrine directly in the 2005 case of City of Sherrill v. Oneida Nation, which concerned the nation’s attempt to regain ancestral lands. The ruling determined that because the doctrine of discovery was “accepted” by the court, title to the land was vested with European colonists and, later, U.S. governments. In other words, repurchasing ancestral lands didn’t restore tribal sovereignty.

In 2005, University of California at Los Angeles law professor Stuart Banner noted that Johnson v. M’Intosh is “treated as one of the cornerstones of American law.” Law students learn to critique the ruling, just as they do other infamous landmark cases from the 19th century, such as Dred Scott v. Sandford, in which Chief Justice Roger B. Taney famously ruled that black Americans weren’t citizens. But while the Dred Scott ruling was eventually overturned, the Johnson ruling is still on the books and still being cited by the court.

We can also hear echoes of the doctrine in a common refrain heard during the 2016 presidential election: that white Christian Americans "want their country back” — the assumption being that the United States and the land it occupies was theirs to lose. The phrase raises a host of questions: Who “took” it? When was it lost? Which losses matter? And who can — and cannot — make claims in the first place?

These are questions the doctrine of discovery and all the legal decisions that are based on it have tried to solve. The fact that the issue has never gone away is a testament to the centuries-long struggle indigenous nations and peoples have endured — and endure to this day.

The doctrine of discovery forces us to engage with uncomfortable truths that predate the existence of the United States yet still shape the present. Which is why Protestant churches turning their repudiation into action is as symbolically significant as it is overdue. There’s still much to be done. One glaring omission is a repudiation from the Catholic Church. And while denouncing the pernicious doctrine is important, so, too, are the actions churches will take to repent, which some argue should include supporting the Standing Rock Sioux in their campaign against the Dakota Access Pipeline and returning land to indigenous nations.

We live in an era when whitewashed historical narratives are being challenged at a mainstream level. Confederate monuments are finally coming down, and films such as “BlacKkKlansman” are garnering critical acclaim.

So far, these challenges have yet to seriously reckon with colonization. Perhaps the tide is turning. Protestant churches electing to not only repudiate the doctrine, but also act on their repudiation, sends a strong message to Americans — more than a quarter of whom identify as evangelical Protestants — that rejecting the doctrine and the legal arguments that stem from it is long overdue. This doesn’t just help correct a historical injustice; it also starts to imagine a future in which Native Americans are seen as the rightful owners of the land on which those of us who are non-indigenous are the occupiers — not them.