President Donald Trump's decision to declare a national emergency to fund a border wall between the U.S. and Mexico could allow future presidents to use emergency powers to address climate change, legal experts said.

But the success of that strategy will depend on whether the courts back Trump's order and if Congress reforms the National Emergencies Act to give curb presidents' emergency powers.

Trump announced Feb. 15 that he will declare a national emergency to unlock more federal resources to build a wall along the U.S.-Mexico border, citing security and humanitarian concerns. As part of the declaration, Trump invoked a handful of federal statutes to direct the secretary of defense and the heads of other agencies to help build the wall and implement other border security measures.

The move came after the U.S. Congress rejected Trump's request to include $5.7 billion for border security in a recent appropriations bill. It has worried some GOP lawmakers who fear that future administrations could declare an emergency to act on climate change. Those concerns are particularly acute as progressive members of Congress promote the Green New Deal policy platform aimed at shifting the U.S. away from fossil fuel-based electricity.

A national emergency declaration "certainly could be done in relation to climate change," said Andrew Boyle, counsel for the Liberty and National Security Program at the New York University School of Law's Brennan Center for Justice.

The Brennan Center compiled a list of statutes that give presidents special powers during emergencies. Among other things, the president can suspend oil leases during national emergencies, an authority the White House could use to address global warming.

"If climate change is a national emergency caused by fossil fuels, then suspension [of those leases] seems like a logical response," said Dan Farber, co-director of the Center for Law, Energy and the Environment at the University of California-Berkeley School of Law.

Presidents also have the authority to respond to industrial supply shortfalls during emergencies, which could allow them to expand battery or electric vehicle production or extend loan guarantees to renewable energy projects if they declare a climate emergency, Farber said.

Furthermore, the International Emergency Economic Powers Act allows presidents to impose sanctions or regulate financial transactions to address extraordinary threats from outside the U.S. In the event of a climate emergency, "these powers could be deployed against companies or countries trafficking in fossil fuels," Farber added.

Court challenges

Attacking the basis of an emergency declaration is difficult because the National Emergencies Act does not clearly define what constitutes an emergency, and courts often defer to the executive branch's determinations, Boyle said. But the underlying legal statutes presidents use to address emergencies is "where the rubber is going to hit the road" on court challenges.

A coalition of 16 states has already filed a lawsuit against Trump's emergency declaration, arguing the president would divert funds Congress already appropriated for other purposes toward a border wall for which Congress has not provided the desired money.

Similar arguments could be used to challenge national emergencies for climate change, particularly given the steep costs of such action.

"If you're talking about replacing all the coal plants in the US with solar … that's going to cost hundreds of billions of dollars that Congress has not appropriated for that purpose," said Neil Bhatiya, an associate fellow with the Center for a New American Security's Energy, Economics, and Security program. "That strikes me as a fairly straight-forward and winnable legal challenge."

Potential statutory reforms

Potential changes to the National Emergencies Act could also thwart future efforts to address climate change through a national emergency declaration.

Emergency declarations expire after one year, but presidents can renew them indefinitely. The National Emergencies Act, enacted in 1976, originally allowed Congress to terminate a state of emergency with backing from a simple majority in the U.S. Senate and House of Representatives. That requirement was found unconstitutional in 1983, meaning the president must now sign off on any measure from Congress to end an emergency declaration, effectively requiring the proposal to pass with a veto-proof majority to avoid being struck down by the president.

Critics said that as a result, the law grants presidents too much power and should be updated.

"Congress should replace this weak backstop with the system used by many other countries: The head of state can declare an emergency, but it is strictly time-limited, and only the legislature can renew it," said Elizabeth Goitein, co-director of the Brennan Center's Liberty and National Security Program. "This approach would eliminate the perverse incentives that exist when the government actor who declares the emergency is the same one receiving the enhanced powers."