Cooley v. Board of Wardens
A Pennsylvania law required all ships entering or leaving Pennsylvania to hire a local pilot or pay half the pilotage fee, which conflicts with Congress' power to regulate interstate commerce. Cooley violated the state law.
The Pennsylvania courts found Cooley liable for the penalty.
Can states regulate interstate commerce?
A federal law was previously passed saying that pilots shall be regulated in conformity with states' laws. If the Constitution divested the states of the power to regulate interstate commerce, this act could not have given it back to them, so it implies that they already had it. Congress only needs exclusive jurisdiction when the matter is of a national nature. Here, pilotage only concerns local matters, so the state should be able to regulate it even if it is a matter of interstate commerce.
Yes, states can regulate interstate commerce. Affirmed.