Because congress uses broad definition of the power to regulate commerce

The correct is that as a result of the broadening definition of interstate commerce, Congress is able to get involved in more "commerce" matters.

The broadening of this really began under the seminal SCOTUS case Wickard v. Fillburn. Since Wickard, Congress has deemed it appropriate to get involved in things such as guns in schools, although the Supreme Court did strike that down.

Regardless, Congress is much more involved than they were pre 1940s.

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