An interesting battle shaping up on the MA/NH border has state governments knocking heads. The issue at point is MA state revenue agents trying to get sales data from a NH store regarding who purchased merchandise as MA residents and brought those products back over the border (they want to collect sales tax on items purchased in NH by MA residents).
NH lawmakers just passed a law making it more difficult for out of state revenue agents to collect this data. However, according to some commenters, the requirement to tax out of state purchases violates the US Constitution (not that politicians care about that old rag anyway). I am not sure exactly how all this works, but it is very interesting and warrants further study.