President Donald Trump's first Supreme Court pick, Justice Neil Gorsuch, has established himself as a reliable conservative on the bench.

But on one issue, the Colorado native has sided with the court's liberals more than once: Strengthening the treaty rights of Native American tribes.

Twice this term, including in a decision handed down on Monday, Gorsuch has signed onto 5-4 rulings that entrenched the rights of Native American tribes under 19th-century treaties.

Those votes, the only 5-4 splits on Native American issues since Gorsuch was confirmed in 2017, have put him at odds with the conservative wing of the bench, including its newest member and fellow Trump appointee, Justice Brett Kavanaugh.

The divergence between Gorsuch and Kavanaugh, who were both vetted by the Federalist Society, could have something to do with geography. Gorsuch was born in Denver and later served as a judge on the Denver-based 10th Circuit Court of Appeals, which has jurisdiction over much of the nation's West and hears cases concerning Native American laws regularly. Kavanaugh, like the other conservatives on the court, was born, and later served as an appeals court judge, on the nation's East Coast.

The two decisions this term both emerged from disputes arising in Western states, Washington and Wyoming.

On Monday, the court affirmed the right of the Crow Tribe to hunt in the Bighorn Mountains, a range that straddles Wyoming and Montana, under the terms of an 1868 treaty. Gorsuch joined with the four liberals on the bench to sign onto an opinion written by Justice Sonia Sotomayor. The opinion clarified that treaties signed in territories that later became states cannot be terminated simply on the basis of statehood.

In March, Gorsuch joined the same majority, in a case concerning the Yakama tribe's importation of fuel into the state of Washington. While Gorsuch did not outline his thinking in Monday's case, in March, he tangled with Kavanaugh in a concurrence that took issue with the newest justice's dissent on a variety of matters.

In that case, Washington State v. Cougar Den, Gorsuch teamed up with the senior member of the court's liberal wing, Justice Ruth Bader Ginsburg, to argue that an 1855 treaty barred Washington from taxing the Yakama tribe for bringing in gasoline from out of state.

"To some modern ears, the right to travel in common with others might seem merely a right to use the roads subject to the same taxes and regulations as everyone else," Gorsuch wrote, citing Kavanaugh's dissent. "But that is not how the Yakamas understood the treaty's terms."

Gorsuch and Ginsburg, an unlikely duo in most matters, argued that the decisive factor in the case was what the Yakama tribe believed they were agreeing to at the time they signed the treaty.

The top court is set to decide one more Native American treaty case this term.

In November, the justices heard the case of a Creek Nation tribe member who is challenging his murder conviction on the grounds that the alleged killing took place on a reservation and therefore outside the jurisdiction of Oklahoma courts.

The question originally put before the court was whether 1866 territorial boundaries of the Creek Nation constitute a reservation. But after arguments, the justices asked for more information about whether, if the area does qualify as a reservation, there is any statute that could still provide Oklahoma jurisdiction.

A decision in that matter is expected by July.