It is, of course, but that doesn't mean California can't regulate it; simply that federal laws take precedence. If states couldn't regulate interstate commerce

It is, of course, but that doesn't mean California can't regulate it; simply that federal laws take precedence. If states couldn't regulate interstate commerce taking place in their own states, they effectively couldn't regulate any commerce because court decisions have found that essentially all economic activity, even growing food for your own consumption, falls under the banner of interstate commerce.