A federal appeals court on Friday upheld a rule prohibiting roads on nearly 50 million acres of land in national forests across the United States, a ruling hailed by environmentalists as one of the most significant in decades.

Mining and energy companies, however, say it could limit development of natural resources such as coal, oil and natural gas.

The 10th U.S. Circuit Court of Appeals backed the 2001 Roadless Area Conservation Rule after lawyers for the state of Wyoming and the Colorado Mining Association contended it was a violation of the law.

Supporters of the roadless rule say the court’s decision preserves areas where outdoor enthusiasts like to hunt, fish, hike and camp. It also protects water quality and wildlife habitat for grizzly bears, lynx and Pacific salmon, supporters say.

“Without the roadless rule, protection of these national forests would be left to a patchwork management system that in the past resulted in millions of acres lost to logging, drilling and other industrial development,” said Jane Danowitz, director of the Pew Environment Group’s U.S. public lands program.

“The public forests we’ve fought so hard to protect are now safe,” added Tim Preso, an Earthjustice attorney for the conservation groups.

U.S. Forest Service Chief Thomas Tidwell also applauded the decision.

The Colorado Mining Association was reviewing its next steps involving the roadless rule.

In a statement, the association said it was disappointed that the ruling does not reflect a practical understanding of the impact on mining jobs or energy needs.

“It is important to develop high-quality coal and other mineral reserves impacted by this regulation here in the United States and in Colorado, both to ensure our nation’s energy security and reduce our dependence on minerals produced in other countries,” the statement said.

The U.S. Forest Service currently manages more than 190 million acres of land used for multiple purposes that must comply with strict rules on land use changes spelled out in the federal Wilderness Act and National Environmental Policy Act.

Renny MacKay, spokesman for Gov. Matt Mead (R-Wyo.), said the state has not decided whether to appeal the ruling made Friday.

“This is a lengthy and significant decision, and Gov. Mead will be evaluating the options for Wyoming over the coming weeks,” MacKay said.

The roadless rule was put in place by the Clinton administration in 2001, not long before George W. Bush took office as president. The rule followed more than two years of public hearings and 1.6 million comments.

Two other legal actions to protect roadless areas are pending, including a lawsuit contesting application of the roadless rule to national forests in Alaska, and a suit challenging a separate, less protective rule that applies only to areas of Idaho.

— Associated Press