The president previously threatened to use emergency powers to impose tariffs on Mexican goods, unless the Mexican government did more to stop migrants from illegally entering the United States. He backed off after Mexico promised to take tougher action.
His effort to use 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.
The law was passed to define and restrain presidential power, which until then had been seen by critics as interpreted too expansively. It has served ever since as the main source of authority for presidents to sanction other countries or individuals in response to specific national security threats, such as the Iranian hostage crisis that began in 1979.
As of March 1, presidents had declared 54 national emergencies under the law, of which 29 were still active, according to the Congressional Research Service. Among others, presidents have used it to target international terrorists, drug kingpins, human rights abusers, cyber attackers, illegal arms proliferators, and multinational criminal organizations.
Presidents relied on the law’s authority when Iraq invaded Kuwait in 1990, when Serbia sent troops into Kosovo in 1998 and when Russia annexed Crimea in 2014. Among the countries targeted at various points over the years have been international outliers like North Korea, Sudan, Somalia, Yemen, Syria, Congo and Venezuela.
Seeking to use it in a trade dispute with a country like China would be a drastic departure from its history. But Mr. Trump could make the argument that China’s theft of intellectual property constitutes a national security threat akin to cyber attacks or other nonviolent attacks on American sovereignty.