“I’m going to change the regulatory and permitting process,” Mr. Romney said Thursday at a rally in Hobbs, N.M., in the giant Permian Basin oil fields, where companies are eager to begin drilling on millions of acres of federal lands. “Sometimes I have the impression that the whole regulatory attitude of the administration is trying to stop oil and gas and coal — that they don’t want those sources, that instead they want to get those things so expensive and so rare that wind and solar become highly cost-effective and efficient.”

Giving states control over the energy resources on millions of acres of federal lands would be a radical shift from decades of policies under both Democratic and Republican presidents, dating all the way to Theodore Roosevelt, who first set aside vast tracts of territory to preserve wildlife. Since then, the federal government has tried to balance exploitation of mineral resources with other uses like recreation and environmental protection.

“This step would be a change in national policy direction going back at least 50 years, giving control over national assets to localities,” said Michael E. Webber, associate director of the Center for International Energy and Environmental Policy at the University of Texas at Austin. “Local decision makers could inhibit production that could be against the national interest or could encourage production that could pollute waters or air in another state.”

Mr. Romney said that states like North Dakota and Colorado grant drilling permits on state-owned lands in days or weeks, compared with the nearly a year that it takes the federal government to grant approval. “They found a way to do a job in a more efficient way,” he said. “On federal lands, the permitting process to actually drill and get oil or gas is extraordinarily slow.”

The Romney campaign acknowledged that such a significant policy change would require the approval of Congress. Getting such legislation passed, even if Republicans controlled the House and the Senate, would be very difficult, given certain opposition by Democrats and perhaps even some Republicans.