Gregory Korte

USA TODAY

WASHINGTON — The president of the United States can't exercise emergency powers without publicly declaring a state of emergency and notifying Congress, the Justice Department has concluded in a newly released legal opinion.

That interpretation reverses a 34-year-old opinion from the Reagan-era Justice Department that held the National Emergencies Act of 1976 applied only to emergency powers that expressly required a presidential declaration.

That opinion, if allowed to stand, could have allowed future presidents to exercise broad powers over the economy, the environment, and the military without oversight — or possibly even the knowledge of — Congress.

The new opinion came in a memo from the Justice Department's Office of Legal Counsel to the White House's top lawyer, and is binding on the executive branch unless rejected by the attorney general or the president. The memo is dated Aug. 24 but was not publicly released until last week, suggesting the White House has signed off on the interpretation.

It's unclear whether the opinion was prompted by any specific emergency, and the White House would not comment on why it requested the review. But the opinion noted that there had previously been "conflicting guidance" on the question. And it said the executive branch had never exercised an emergency power under an undeclared state of emergency since 1976.

There are now 30 national emergencies now in effect, declared through proclamations and executive orders by presidents from Jimmy Carter to Barack Obama. Under the National Emergencies Act, Congress is required to review each emergency every six months, but has never done so. The law also says that emergency declarations expire after a year unless renewed by the president.

Special report: America's perpetual state of emergency

Such emergencies are most often used to impose sanctions on foreign countries and freeze the assets of foreign nationals in the United States. But they can also be used to call up the national guard, waive environmental protections, change federal hiring and pay laws and suspend wage, health and safety protections for workers.

Attorney Patrick Thronson identified 160 such powers in a 2014 article in theUniversity of Michigan Journal of Law Reform. The issue confronted by the Obama Justice Department: Which of those powers require the president to declare a state of national emergency: All of them, or just those that specifically require a declaration?

Thronson said even if Congress has never exercised meaningful oversight over the president's emergency powers, the opinion provides "at least the possibility" that Congress and the public would be aware of how the president is exercising them.

"This was a key concern for the framers of the legislation in the '70s. Congress did not appreciate until that point that substantial portions of government policy were being carried out on the basis of emergencies declared decades earlier," he said.

But the Ford and Reagan administrations took a different view. "Laws like the Defense Production Act of 1950, which do not require a Presidential declaration of emergency for their use, are not affected by this title — even though they may be referred to in a lay sense as 'emergency' statutes."

That was the testimony of President Gerald Ford's assistant attorney general — and future Supreme Court justice — Antonin Scalia, in 1976.

In 1982, the Congress asked the Reagan administration for a report on what authorities the president had to deal with a severe energy disruption. The Justice Department said the president could call up the executive reserve — a volunteer corps of professionals, union members and academics — to serve in the Energy Department. And even though the law allows that action only "during periods of emergency," the Justice Department said the president didn't need to declare an emergency and trigger the National Emergencies Act.

Ted Olson, the assistant attorney general who wrote that opinion said that opinion came in a footnote that was part of "a very lengthy analysis of presidential authorities" requested by Congress.

"Had Congress chosen to correct any misinterpretation of any of its enactments contained in the opinion, it was certainly in a position to do so during the succeeding 30-plus years," Olson told USA TODAY in an email. "But there may not have been any real occasion or impetus to do so."

But Olson, who later served as the solicitor general under President George W. Bush, he also said he wouldn't second-guess the Obama administration opinion. "I assume that the current OLC lawyers looked this over carefully and I have no reason at this distance in time, and without digging into the issues thoroughly, to doubt or fault their analysis," he said.