A quick clarification about the doctrinal framework for analyzing dormant Commerce Clause problems. Yesterday, a couple of you asked this question: if a state successfully demonstrates that it has no nondiscriminatory alternatives to accomplish the objectives of the law, must the state still demonstrate (under the balancing test of Pike v. Bruce Church) that the law's burden on interstate commerce is not "clearly excessive" relative to its putative benefits? The practical answer is no.
In essence, the Court has created a two-tiered scheme of judicial scrutiny for laws challenged under the dormant Commerce Clause. If the state law discriminates against interstate commerce (whether on its face, in its purpose, or in its practical effect), it is subject to the "strictest of scrutiny" and will only be constitutional if the state demonstrates that the law (a) advances legitimate (i.e., non-protectionist) interests, and (b) the state has no other, nondiscriminatory alternatives for accomplishing those goals.
If the state law does not discriminate against interstate commerce, it is subject to a much milder, more deferential standard of scrutiny: it will only be invalidated if it places burdens on interstate commerce that are "clearly excessive" relative to its putative benefits.
The Court has always conceived of these as alternative paths, with one being much stricter than the other. Thus, if a state law survives the stricter test (for discriminatory laws), then a fortiori it should follow that the law satisfies the more deferential Pike balancing test.