What's up with Pennsylvania's fireworks laws?

In Pennyslvania it is illegal to set off any fireworks that fly through the air or explode. Since passage of a law in 2004, however, it is legal for businesses in Pennsylvania to sell such fireworks to non-Pennsylvania residents. The result is the scene that unfolded yesterday.

A friend with a Maryland ID and I went to a fireworks store just barely on the Pennsylvania side of the Pennsylvania-Maryland border. At the front of the store is a small section selling snakes and sparklers and such - the types of fireworks Pennsylvanians are allowed to have. Then there's a roped-off back room, access to which is monitored by a salesperson. My friend presented his Maryland ID and signed an affidavit of some kind and was allowed in. They let me tag along basically as his guest. Oh, the selection of pyrotechnics available in that room! Rockets, fountains, everything this side of a professional fireworks display. We - er, I mean, he - bought $50 worth and, I imagine, had a heckuva show on the Fourth. Law-abiding Pennsylvanians, meanwhile, had to be content running around with sparklers.

In what bizarre world is this arrangement logical or constitutional? How is it that a store in Pennsylvania can let out-of-staters but not in-staters buy its product? Isn't this an unconstitutional restriction on interstate commerce, or a violation of equal protection under the law?

Meanwhile, just across the border in Maryland there's a good beer-wine-liquor store that sells all sorts of wine that is unavailable in Pennsylvania's state-owned wine-liquor stores, and sells beer by the six-pack, unlike Pennsylvania beer stores that are required to sell only by the case. If you buy your hooch in the Maryland store and then drive along the highway back into Pennsylvania, there's a good chance you'll get stopped and fined for transporting alochol across state lines. I'm assured, however, that there's a back way home to Pennsylvania...