JON REISMAN WRITES that state efforts to, in essence, adopt the Kyoto Protocol are assuming powers that belong to the federal government, not the states, under the Constitution.
He's pretty clearly right about this: two former students of mine wrote an excellent article on state foreign-policy efforts in Foreign Affairs a couple of years ago that made the same point. Their article focused on efforts to sanction Burma/Myanmar (which, constitutional issues aside, I would favor) but the point is the same. Foreign policy is messy enough without the states getting involved, particularly as the states who do get involved often aren't the ones who would bear the brunt of any consequences.
Fixing potlholes and funding education should be the responsibility of state and local governments. Foreign policy should be the responsibility of the feds. Neither is doing so superbly in its assigned sphere that it can afford to spend time poaching on the other's turf, however politically appealing such efforts might be.