The Federal Everything Clause
The US government has never been willing to let mere technicalities impede its actions, as has been evident since at least the reign of Andrew Jackson. Judges are both aware of this and unlikely in any case to fight too hard against the system that has put this in place, and so at the higher levels their job description is something like “convincingly rationalize why the government can do as it pleases”—as can be seen in this article on how much the “Federal Commerce Clause” covers.