A state may not discriminate against other states’ articles of commerce on the basis of origin. i.e. Regardless of it’s ultimate purpose, a State may not discriminate against articles of commerce coming from outside the state unless there is some reason, apart from their origin, to treat them differently. E.g. quarantining diseased livestock is OK. State legislatures. If a State law is basically a protectionist measure, it will be unconstitutional. If a State law can be fairly viewed as a law directed to legitimate local concerns, with effects upon interstate commerce that are only incidental, then it will be constitutional. NJ state law prohibited out of state waste from being deposited in NJ landfills because the state was concerned with environmental harm to NJ, as well as running out of space to store waste.
Same rule, different words: 1) if a state law discriminates against an out of state interest it is virtually per se unconstitutional 2) if the law does not discriminate it will still be struck-down if it places an unreasonable burden on I/C relative to any local benefit. Under 1) Court will use strict scrutiny in adjudicating whether a level of discrimination is permissible depending on how legitimate and critical the local purpose is, and whether or not there are reasonable non-discriminatory means available to attain the same purpose. Under this test, the court will apply its own rational basis review and will not be deferential to the empirical findings of the state legislature. Under 2) the court will balance the local benefit against the burden on I/C, and be much more deferential to the state interest.