Democratic White House hopefuls are rolling out aggressive climate change plans that show a sharp break from former President Barack Obama by seeking to prohibit new fossil fuel production on federal lands.

That represents a U-turn from the Trump administration's focus on driving up U.S. fossil fuel production and would go further than climate policies implemented by Obama, who often extolled the rising U.S. energy production from fracking during his tenure in the White House.

All 10 candidates participating in CNN’s climate change town hall Wednesday, including former Vice President Joe Biden and Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.), have proposed halting new leases to tap into energy deposits on millions of acres both onshore and off the coasts, a sign that the party has adopted the position of green groups that long pushed to keep fossil fuels in the ground.

“Everything has gone to 11,” said Kathleen Sgamma, president of the Western Energy Alliance, a group of oil and gas companies. “You pick a topic and it’s like President Obama might as well have been a Republican.”

Federal land is one of few areas where an administration can shift energy development in a major way without relying on action from Congress. Fossil fuels from lands under the federal government's control accounted for about one-quarter of U.S. carbon dioxide emissions between 2005 and 2014, according to the U.S. Geological Survey. It’s also a cash cow: revenues from federal oil and gas output topped $8 billion in 2018, according to the Office of Natural Resources Revenue.

But as the latest reports from scientists in groups like the U.N. Intergovernmental Panel on Climate Change ramp up warnings that time is running short to avoid catastrophic warming, a new group of young activists in organizations like the Sunrise Movement have joined older environmental groups to press Democrats to take aggressive steps.

“President Obama was a friendly target for climate campaigning, but he was never the climate champion we needed. We should have seen the promises candidates are making now a decade ago,” said Jenny Marienau, political campaign director with 350Action.

Energy lobbyists say instituting an outright ban through executive order or some other policy mechanism would likely violate several laws — though that hasn’t dissuaded candidates such as Warren, who said she would issue a moratorium on new leases her first day in office.

And a president can't simply evict energy companies from ongoing operations on federal land without giving them compensation, so the thousands of existing leases would likely remain in place. Companies can also hold onto leases for 10 years at a time.

“Almost every candidate has committed to immediately or rapidly ending leasing on public land and we trust that they’ll find the mechanisms,” Marienau said.

Some candidates have acknowledged that legal obstacle on canceling existing leases, and Warren and Biden have said they would block only new fossil fuel leasing. But Sanders’ climate plan said he would “immediately end all new and existing fossil fuel extraction on federal public lands,” while Sen. Kamala Harris (D-Calif.) envisions "phasing out" existing leases.

Energy lobbyists and attorneys acknowledge that a president has many ways to frustrate energy companies within the confines of the laws.

The Mineral Leasing Act encourages, but doesn’t require, leasing federal land for mineral development. The Federal Land Policy and Management Act promotes using land for multiple purposes, but doesn’t dictate how. The Outer Continental Shelf Lands Act directs leasing of offshore waters for energy development “in a manner which is consistent with the maintenance of competition and other national needs.”

“A new president could certainly make it much more difficult to drill and produce on federal land, but an outright pulling of the emergency brake is going to be very difficult to implement,” said Larry Nettles, an environmental law attorney at Vinson & Elkins LLP in Houston.

The Obama administration exploited that legal latitude, adding carbon costs to environmental reviews and other hurdles for fossil fuel projects. It required rounds of public meetings for finalizing federal land management plans. It proposed new rules on oil and gas producers to reduce methane pollution on federal land.

Though the Trump has gutted those policies since taking office, they could make a comeback.

“If you’re looking at what a Democratic president could do, they could do many of the same things that were done at the end of the Obama administration to burden the leasing process,” Nettles said. “Producers will go elsewhere. And indeed that’s what they did in the Obama administration.”

Shutting down new or even existing drilling on federal land would have little impact on overall U.S production, since the vast majority of oil and gas production is on private land in Texas, North Dakota and other states, said Pavel Molchanov, energy analyst at Raymond James. Any such ban would also be in danger of being reversed when a new administration comes in.

Overall oil and gas production on federal land fell every year between 2009 and 2017, according to the Congressional Research Service. That downturn came as companies poured money in fracking at shale fields that lied largely on private land rather than places like the Gulf of Mexico. Less than a quarter of U.S. oil production comes from federal acreage currently, and only about 13 percent of natural gas.

“Regulatory changes are not only limited in scope, but limited in time,” Molchanov said. “It can be undone just as easily it as originally done. Anything truly game changing would have to get through Congress.”

House Democrats have sought to take on the issue. The House Rules Committee announced on Tuesday that next week it would consider amendments to extend a moratorium on drilling in the Eastern Gulf of Mexico, prohibit energy development in the Arctic National Wildlife Refuge and prevent exploration off the Atlantic and Pacific coasts.

Those efforts aren't likely to advance in the Republican-held Senate, which polls suggest will remain in GOP control after 2020. Without help from Congress, there are limits to what a Democratic president could actually do to eliminate federal oil, gas and coal production.

“I can see them finding it very difficult to implement it and focusing on other issues,” said McKie Campbell, a former staff director for Republicans on the Senate Energy and Natural Resources Committee. “I think both sides have gone towards extremes, which is very bad. Right now there is tremendous pressure to sort of swear allegiance to things.”

Biden, Warren, Sanders and others have said they’d bring back and strengthen Obama’s methane rules. They have also pledged to prioritize wildlife conservation over energy development, a policy maneuver that could effectively shut out oil, gas and coal, Nettles said.

Some candidates, such as Biden and South Bend Mayor Pete Buttigieg, have also suggested they would raise royalty rates for existing leases, increasing how much companies pay the federal government for energy they sell from public lands. Biden said he wants those rates to reflect the cost of climate change.

But the party’s environmental faction warned that simply returning to an Obama climate strategy won’t cut it.

“There is a pitfall now by candidates saying we are going to undo everything the Trump administration has done and go back to the Obama policies, because they were never strong enough,” Marienau said.

Flexing agency discretion in those ways can make it “very difficult” to operate on federal land, said Dan Naatz, senior vice president of government relations and political affairs with the Independent Petroleum Association of America.

“It certainly has us concerned,” he said. “We’ve got our work cut out for us.”