My point was specifically in regards to labeling, for which it's an awful stretch to call a trade barrier. If a label is "scary" enough to dissuade a potential purchaser, then it seems like the purchaser wasn't really informed about what they might have bought in the first place.

> So they could preempt California from requiring labeling on products shipped from Ohio, or require specific federal labeling on the things that are, but only California gets to decide about the things that never leave California

In my ideal world I'd slightly adjust the framing here. California law should apply to products that are being sold within California, regardless where they may have previously been (yes, that would be a complete repudiation of Wickard v Filburn's declaration that a butterfly flapping its wings is interstate commerce). A California distributor or retail store that gets shipments from Ohio but then sells locally should be required to follow California law about what they're selling, as those sales are occurring wholly in California. Also if Ohio and California can agree on something that differs from federal, then that should also take it out of federal preemption territory. But of Ohio and California cannot agree, and someone in California orders direct from Ohio, only then federal law should step in with preemption.