What is the general effect of the Commerce Clause on state regulation of interstate commerce, and what does preemption mean?

• A. Congress may regulate interstate commerce; state laws that significantly burden or discriminate against interstate commerce may be invalid, and federal law can preempt conflicting state law.
• B. States may regulate interstate commerce freely without federal constraints.
• C. Preemption applies only to criminal statutes.
• D. Commerce Clause prohibits any state regulation of interstate commerce.

Answer: (C)

The key idea is that Congress has the power to regulate interstate commerce, and that power curbs state regulation that affects goods, people, or services moving across state lines. Relatedly, the Dormant Commerce Clause prevents states from enacting laws that discriminate against or unduly burden interstate commerce. When federal law conflicts with state law, the Supremacy Clause allows the federal rule to preempt the state rule, so the federal standard prevails.

This is why the best answer states that Congress may regulate interstate commerce; state laws that significantly burden or discriminate against that commerce may be invalid, and federal law can preempt conflicting state law. The other options are inaccurate: states don’t regulate interstate commerce without federal constraints; preemption applies to more than just criminal statutes; and the Commerce Clause does not prohibit all state regulation of interstate commerce.