Re: "Where in the Constitution..?"
I suggest you do a little research. The Commerce Clause had a specific function, and despite "interpretations," was not intended to mean "The Federal Government has absolute power over every economic activity in the nation." It has evolved to this, thanks to various courts, but then those are the same sort of courts that declared it "constitutional" to haul American citizens of Japanese descent off to camps solely because of their race, among other things.