BIARRITZ, France — President Trump asserted on Saturday that he has the authority to make good on his threat to force all American businesses to leave China, citing a national security law that has been used mainly to target terrorists, drug traffickers and outlier states like Iran, Syria and Libya.
As he arrived in France for the annual meeting of the Group of 7 powers, Mr. Trump posted a message on Twitter citing the International Emergency Economic Powers Act of 1977, a law originally passed as part of a congressional effort to define and restrain presidential assertions of power not to enable a president to cut off economic ties with a trading partner because of a disagreement over tariffs.
“For all of the Fake News Reporters that don’t have a clue as to what the law is relative to Presidential powers, China, etc., try looking at the Emergency Economic Powers Act of 1977,” Mr. Trump wrote. “Case closed!”
“Our great American companies are hereby ordered to immediately start looking for an alternative to China, including bringing our companies HOME and making your products in the USA,” Mr. Trump tweeted, adding, “We don’t need China and, frankly, would be far better off without them.”
Mr. Trump’s threat to invoke the 1977 act to force companies to leave China would be his most recent unorthodox use of standby authorities that Congress delegated to the presidency for exigent circumstances. The president previously threatened to use those emergency powers to impose tariffs on Mexican goods, unless the Mexican government did more to stop migrants from illegally entering the United States.
The president’s tweet could further unsettle American companies that conduct an enormous amount of business with China, one of the United States’ largest trading partners. Stock markets fell sharply on Friday after Mr. Trump first raised the prospect of cutting off trade altogether.
His effort to use the emergency powers could also be challenged in court, given the restrictions surrounding when it can be invoked. The International Emergency Economic Powers Act says that if the president decides that circumstances abroad have created “any unusual and extraordinary threat” to “the national security, foreign policy, or economy of the United States,” the president can declare a “national emergency.” This triggers special authority for the leader to regulate “any transactions in foreign exchange” by Americans.