https://www.siliconvalley.com/2019/05/15/trump-declares-national-emergency-around-telecom-networks/

WASHINGTON – President Donald Trump on Wednesday signed an executive order declaring a national emergency and barring U.S. companies from using telecommunications equipment made by firms posing a national security risk, paving the way for a ban on doing business with China’s Huawei Technologies Co.

The executive order invokes the International Emergency Economic Powers Act, which gives the president the authority to regulate commerce in response to a national emergency that threatens the United States. The order directs the Commerce Department, working with other government agencies, to draw up a plan for enforcement within 150 days.