I think Article I section 8 may also apply, specifically the Commerce clause: > The Congress shall have Power [...] To regulate Commerce with foreign Nations

I think Article I section 8 may also apply, specifically the Commerce clause: > The Congress shall have Power [...] To regulate Commerce with foreign Nations A state prohibiting or requiring the purchase of goods from a particular foreign nation would seem to be encroaching on a Federal power. Especially if this bit gets interpreted as broadly as the next bit does (regulating commerce "among the several States").