When regulating private activity, Congress can give states the choice of regulating according to federal standards or having the federal government preempt state regulation. The Congress shall have Power . . . To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes. The Commerce Clause gives Congress exclusive authority to regulate interstate commerce.
Congressional inaction is a form of regulation so preempts state regulation.
States may not unreasonably interfere with interstate commerce. Regulating matters of local concern or matters that demand uniform national rules. The goal of a truly integrated country in which states are working together. The goal of a well-functioning national economy. If an even-handed effect on intrastate and interstate commerce, and effects on interstate commerce are incidental, statute allowed unless burdens on interstate commerce clearly excessive in relation to local benefits.