The Tax Cuts and Jobs Act, which the Senate passed early Saturday morning, will change federal law on a matter that has little to do with the tax code. The bill authorizes the sale of oil and gas leases in a section of the ANWR on Alaska’s North Slope, the coastal plain that faces the Arctic Ocean. Soon, energy companies will be able to search for—and extract—oil and gas from the frozen tundra.

The Senate bill will now be reconciled with the House version in conference and go to President Donald Trump’s desk for his signature.

It brings a quiet end to the battle over whether to drill in the ANWR, one of the longest-running and most acrimonious battles in U.S. environmental history. The question has been embedded in federal law for 40 years, nearly as long as Alaska has been a state.

No one will be more affected by the opening of ANWR than Alaska’s indigenous people, who will live among—and work on—the rigs, drills, and pipelines that would follow the discovery of any oil or gas reserve. The discovery of oil or gas in the region could bring an economic windfall to the subsistence tribes that live on Alaska’s North Slope, the coastal plain that faces the Arctic Ocean. But if a major disaster—like an oil spill or a gas leak—were to occur in the area, it would devastate their only homeland.

The issue still divides villages, counties, and Native nations in Alaska. It also sets tribes with differing claims to Alaska’s North Slope against each other. And both sides tend to assert that the overall public sides with them.

“The majority of Alaskans and majority of Alaksa Natives express their support for [drilling in ANWR]. It’s an issue of economic self-determination for our community,” said Richard Glenn, a member of the Inupiat tribe and the executive vice president of the Arctic Slope Regional Corporation, which owns nearly 5 million acres across Alaska’s northern coast. “This has been the unchanging position of the majority of the residents of our region for more 30 years.”

No recent polling data seems to be available on the issue. But even beyond public opinion, there’s a basic conflict.

The Inupiat live across the North Slope, including within the part of the ANWR that would soon be opened for drilling. Oil exploration already brings jobs and funds infrastructure in their communities. And the Arctic Slope Regional Corporation holds mineral rights to pockets of private land within the ANWR. If oil is discovered there, the corporation and its shareholders—roughly 13,00 members of the Inupiat tribe—could profit from the wealth.

The Gwich’in people, meanwhile, live hundreds of miles south in west-central Alaska. Their regional corporation does not own land on the North Slope. But the Gwich’in are spiritually connected to the porcupine caribou, a herd of more than 160,000 creatures who migrate annually across the U.S. and Canadian tundra. The herd’s calving grounds, the most sacred space to the Gwich’in, lies within the area which could soon be open to drilling. To many of them, drilling in the calving ground isn’t just an attack on the Gwich’in way of life. It’s an attack on the Gwich’in.