Daniel,
found this hope it helps
http://law2.umkc.edu/faculty/projects/ftrials/conlaw/statecommerce.htm
Baldwin v G. A. F. Seelig (1935) invalidated a New York law prohibiting the sale in the state of New York of milk bought outside of New York. New York argued the law was necessary to avoid price competition that would drive dairies into producing less wholesome milk. The Court, more realistically, saw the law as protectionist. Justice Cardozo wrote that when "a state tries to isolate itself economically" it must show an important interest for doing so and that it had no less discriminatory mean open for accomplishing its goal. Cardozo's test has become the standard test for evaluating state laws that discriminate against out-of-state commerce.
In another New York milk case, H. P. Hood and Sons v Dumond (1949), the Court applied the Baldwin test for protectionist laws to the state's denial of a license to operate a depot to collect milk for distribution to Boston. The Court saw the license denial as an effort by New York to horde a resource and thereby keep prices for its consumers low.
Dean Milk Co. v Madison (1951) deals with discrimination against out-of-state (as well as much in-state) commerce not by a state, but by a city. At issue in yet another milk case was a Madison, Wisconsin ordinance that prohibited the sale of milk in Madison that was bottled more than five miles from the city's center. The ordinance was justified by Madison as necessary to facilitate inspection by city dairy inspectors. Finding the ordinance discriminatory and believing that reasonable non-discriminatory alternatives existed, the Supreme Court invalidated the ordinance despite the fact that a Milwaukee dairy was shut out of town just as much as one from Illinois.
Edwards v California (1941) considered a challenge to a California law aimed at reducing the influx of dustbowl indigents to the state. The California statute made it a crime to bring into the state any indigent non-resident. Finding people in this case to be "articles of commerce," the majority found the statute to be a form of unconstitutional discrimination against out-of-state commerce. (Four concurring justices would have preferred to invalidate the law on 14th Amendment privileges and immunities grounds.)
In Philadelphia v New Jersey (1976), the Court struck down a New Jersey law that prohibited the importation of garbage into the state. Concluding that garbage was "commerce," the Court viewed the law--despite its environmental justification--as unconstitutional discrimination agains out-of-state commerce. The Court held that as long as reasonable, non-discriminatory alternatives exist that serve the states legitimate interests, they must be used instead of a discriminatory ban.
In Hughes v Oklahoma (1979), the Court invalidated an Oklahoma law prohibiting the interstate transportation of minnows taken from Oklahoma waters. The Court rejected Oklahoma's law that states "own" wildlife and therefore wildlife is not "an article of commerce." The law could be upheld only if the state could show it served a significant local interest that could not be furthered by a non-discriminatory law--this Oklahoma could not show.
Maine v Taylor (1986) is a rare example of a Supeme Court decision upholding a state statute that discriminated against out-of-state commerce. The Court accepted the trial court's findings that no non-discriminatory alternatives to Maine's ban on the importation of live baitfish adequately served the state's interest in preventing the introduction into Maine waters of new parasites and non-native fish species that might upset Maine's ecosystems.