Absolutely. The constitution prohibits both the US and any state from passing retroactive laws (not that that stopped Bush's 2001 retroactive tax cut or Clinton's retroactive tax hike or anything).
If we were obligated to stick to the Constitution, we wouldn't have career politicians be-holdin' to every special interest known to man today....The People would have the power (which is what the Constitution provides), and the power of the Federal government would be left to the States.