Yes, Congress has given the President the power to “regulate, direct and compel, nullify, void, prevent or prohibit, any acquisition, holding, withholding, use, transfer, withdrawal, transportation, importation or exportation of, or dealing in, or exercising any right, power, or privilege with respect to, or transactions involving, any property in which any foreign country or a national thereof has any interest by any person, or with respect to any property, subject to the jurisdiction of the United States” [1], “to deal with any unusual and extraordinary threat, which has its source in whole or substantial part outside the United States, to the national security, foreign policy, or economy of the United States, if the President declares a national emergency with respect to such threat” [2]. This is the power that Trump is purporting to exercise.

[1] https://www.law.cornell.edu/uscode/text/50/1702

[2] https://www.law.cornell.edu/uscode/text/50/1701