[AnthonyMouse]

Is there a case that considers how this applies to preemption?

For example, could the federal government preempt the states from having public schools, public roads or a police force under the commerce clause because they impact the interstate market for private schools, private roads and private security? It seems like maybe they should only be able to preempt when the thing is actually interstate commerce and not just affecting it. But is there any case deciding that issue one way or the other?

[wahern]

It's hyperbole to say everything effects interstate commerce as a legal matter. See https://en.wikipedia.org/wiki/United_States_v._Lopez, where the court struck down the Federal Gun-Free School Zones Act of 1990.

On the other hand, that's a really low bar for the Federal government to meet. Especially in light of https://en.wikipedia.org/wiki/Gonzales_v._Raich, where the court upheld Federal criminal prohibition of homegrown marijuana for personal use, and where everybody stipulated (IIRC) that her marijuana wouldn't enter the stream of commerce. Note that both Kennedy and Scalia upheld Federal powers here, which is why their vehement opposition to Obamacare's individual mandate was so hypocritical.