The president, via executive order, has given the Commerce Secretary the ability to ban the import of gear and services from companies that have close ties to foreign governments. This could be applied to any of the major telecoms equipment companies, but it is understood to be aimed at Huawei.
The executive order also gives the Commerce Secretary, in consultation with other agencies, the ability to ban damn near anything that he believes "poses an unacceptable risk to the national security of the United States or the security and safety of United States persons."
All that's required, according to the wording of the executive order, is belief. Not proof. Not evidence. Not prior action or sufficient motivation. Just believe whatever you like and you can ban whatever you like.
The point of this exercise is to avoid the disruption of US telecommunications or other infrastructure, according to the president's order. In the first sentence, Trump notes that this is ongoing as he said he's finding "that foreign adversaries are increasingly creating and exploiting vulnerabilities in information and communications technology and services..."
Huawei isn't mentioned in the executive order, but it's clearly aimed at giving the government the all clear to outright ban Huawei gear, as well as to ban the supplying of components and services to Huawei.