Technically I think you're suppose to claim non-taxed goods when you bring them back to your state so they can be taxed... commonly seen if you buy clothes in a state where there is no clothing tax, and bring them back to where there is clothing tax.
I'm not sure what law specifically it applies under, as it destroys part of free enterprise.
An old boss of mine bought a car in another town, and lived in a town that had a 1% higher sales tax. Several weeks after buying the car, he got a letter from the city saying he owed them money for tax on the car-- again I think complete BS, if you bought it in a higher tax area, you should get that 1% tax back then. So he moved outside the city limits after that.
Technically you are supposed to claim them, not sure how you do it, or how they would ever enforce it.
