If I am correct, I think it's the Interstate Commerce Clause[1] of the US Constitution. [1] https://en.wikipedia.org/wiki/Commerce_Clause https://en.wikipedia.

If I am correct, I think it's the Interstate Commerce Clause[1] of the US Constitution. [1] https://en.wikipedia.org/wiki/Commerce_Clause https://en.wikipedia.org/wiki/Commerce_Clause (note that the wiki article is the "Commerce Clause", but it mentions the "Interstate Commerce Clause")