In one of its final rulings of the year, the U.S. Supreme Court released a decision that designates a large portion of Oklahoma as tribal territory.

With the decision in place, significant parts of eastern Oklahoma are now legally considered reservation land where state criminal law does not have jurisdiction. Conservative Justice Neil Gorsuch, an appointee of President Donald Trump, sided with the court's four liberal judges in the landmark decision, according to The New York Times.

The controversial case revolves around Jimcy McGirt, a 71-year-old member of the Seminole Nation who has spent more than two decades in prison since being convicted for raping a 4-year-old in 1997.

McGirt was not contesting his guilt in the charges but challenged the jurisdiction of the state courts. The assault was committed on land that has been claimed by the Muscogee (Creek) Nation, one of the five tribes in Oklahoma. The others are Seminole, Chickasaw, Choctaw and Cherokee tribes.

The Creek Nation and other tribes were forcibly relocated by the U.S. government in the 1800s to reservations in Oklahoma during an event now known as the Trail Of Tears.

For those wondering, here's how much of Oklahoma the Supreme Court ruled the Oklahoma state courts have NO JURISDICTION over this morning (dark red)#Oklahoma
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— Tom McMahan (@TomMcMahanDade) July 9, 2020

"On the far end of the Trail of Tears was a promise. Forced to leave their ancestral lands in Georgia and Alabama, the Creek Nation received assurances that their new lands in the West would be secure forever. In exchange for ceding 'all their land, East of the Mississippi river,' the U.S. government agreed by treaty that “[t]he Creek country west of the Mississippi shall be solemnly guarantied to the Creek Indians,” Gorsuch wrote for the majority opinion.

"Today we are asked whether the land these treaties promised remains an Indian reservation for purposes of federal criminal law. Because Congress has not said otherwise, we hold the government to its word. … If Mr. McGirt and the Tribe are right, the State has no right to prosecute Indians for crimes committed in a portion of Northeastern Oklahoma that includes most of the city of Tulsa. Responsibility to try these matters would fall instead to the federal government and Tribe," he added.

Gorsuch goes on to say, historically, states have routinely flouted laws and treaties passed by Congress that relate to Native Americans. Instead of defending the state court decision on procedural means, Oklahoma officials asked the Supreme Court to "confirm that the land once given to the Creeks is no longer a reservation today."

The Creek Nation joined the case, and Gorsuch said it was clear when the U.S. government signed its treaty with the tribe in 1832 that the land was theirs. The treaty includes a line that states Congress assured the tribe that "the United States will forever secure and guaranty to them" the land. Years later in an 1866 treaty, the U.S. government agreed to buy a portion of the land from the Creek Nation but reaffirmed the natives' sovereignty over the land, writing that it was "forever set apart as a home for said Creek Nation.”

"While there can be no question that Congress established a reservation for the Creek Nation, it’s equally clear that Congress has since broken more than a few of its promises to the Tribe. Not least, the land described in the parties’ treaties, once undivided and held by the Tribe, is now fractured into pieces," Gorsuch said.

With Thursday's ruling, Reuters reported that a number of changes could be made by Native American tribes in the area. More than 1.8 million people live on the lands that were in question in the case, and tribe members may now be exempt from paying state taxes and following other state rules, Reuters noted.

Some Native Americans may be able to challenge charges or cases handled by state courts, and some of the tribes will have more control over how alcohol sales and casinos are regulated.

The SCOTUSBlog account on Twitter wrote that "because Congress failed to formally undo the Muscogee (Creek) Nation's 19th century reservation, the land in eastern Oklahoma remains a Native American reservation for purposes of federal criminal law."

The 3 million acres in eastern Oklahoma will now fall under tribal and federal law. A Creek Nation lawyer told CNBC that McGirt can now be tried by federal authorities for his crime. Reuters reports that the land equates to about half of the state.

In his dissent, Chief Justice John Roberts blasted the decision, saying it will lead to decades of convictions being thrown out and push the state into chaos.

“The State’s ability to prosecute serious crimes will be hobbled and decades of past convictions could well be thrown out. On top of that, the Court has profoundly destabilized the governance of eastern Oklahoma. The decision today creates significant uncertainty for the State’s continuing authority over any area that touches Indian affairs, ranging from zoning and taxation to family and environmental law,” Roberts wrote.

“None of this is warranted. What has gone unquestioned for a century remains true today: A huge portion of Oklahoma is not a Creek Indian reservation. Congress disestablished any reservation in a series of statutes leading up to Oklahoma statehood at the turn of the 19th century. The Court reaches the opposite conclusion only by disregarding the ‘well settled’ approach required by our precedents,” Roberts added.

While state officials have bashed the decision and made outlandish claims about how it would affect state laws, Creek Nation attorney Riyaz Kanji told CNBC that the rhetoric did not match what was actually being decided on.

“I don’t think this case is going to have earth-shattering consequences. It just doesn’t change anything with respect to non-Indians,” Kanji said.

“The Supreme Court reaffirmed today that when the United States makes promises, the courts will keep those promises. Congress persuaded the Creek Nation to walk the Trail of Tears with promises of a reservation — and the Court today correctly recognized that this reservation endures. We — along with our co-counsel Patti Palmer Ghezzi and the Federal Public Defender of the Western District of Oklahoma — are immensely pleased for Jimcy McGirt and Patrick Murphy, whom Oklahoma unlawfully prosecuted for alleged crimes within the Creek reservation,” Ian Heath Gershengorn, the lawyer for McGirt, said in an emailed statement to CNBC.

Despite the inflamed rhetoric, after the ruling was handed down, a joint statement was sent to The Washington Post by Oklahoma Attorney General Mike Hunter and leaders of the five tribes which said the two sides would be working on agreements that outline how the new situation would work legally.

“We have a shared commitment to maintaining public safety and long-term economic prosperity for the Nations and Oklahoma,” the statement read.

Forrest Tahdooahnippah, a lawyer and member of the Comanche Nation, explained to HuffPost what exactly the two sides would have to work out in the new agreement.

“In the long term, outside of the criminal context, there may be some minor changes in civil law, the majority opinion points out assistance with homeland security, historical preservation, schools, highways, clinics, housing, and nutrition programs, as possible changes. The Creek Nation will also have greater jurisdiction over child welfare cases involving tribal members. The short term implications of McGirt are largely confined to the criminal context in which the case arose,” Tahdooahnippah said in a statement.

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