Okay, after much discussion with other people, visits to various consumer sites, and a look at the CPSC's statements on the subject, one thing is clear:

Law is dumb.

In Pennsylvania, it is legal to sell fireworks such as bottle rockets and firecrackers. However, the citizens of PA are not allowed to set these off.

Meanwhile, Virginians are allowed to set off only lower-grade fireworks that are made by that TNT company, and that's all we're allowed to sell.

It just seems so stupid.