Answer:
unconstitutional under the "dormant" commerce clause.
Explanation:
The Commerce Clause (Article 1, Section 8, Clause 3 of US Constitution) state that Congress has the power "to regulate commerce with foreign nations, and among the several states, ..."
The dormant commerce clause refers to limitations on state powers, which cannot pass any law that excessively burdens or discriminates against interstate commerce. Only Congress has the power to regulate interstate commerce.