Is this an executive measure? Does the executive have authority to do such a thing, based on vague and nebulous claims of threat to national security? Were these companies providing sevices/supplying goods in the US market subject to necessary US regulatory approvals? On which grounds can such approvals be rescinded without evidence that will stand in courts?

Moreover this is infact a restriction on US citizens/ firms from buying these goods? Does it not impinge on their rights to fair choice?