Steve the short answer is – check the laws of EVERY state youre driving through. Some states like MA or NJ are really strict even about 1.4G. Others are fine.
General practical advice:
– Keep everything in original packaging, unopened if possible
– Put it in the trunk – not the passenger cabin
– Dont have anything illegal in the state you start in or end in
– If you get pulled over, dont volunteer that you have fireworks. Only mention it if they ask
– Keep receipts if you bought them legally
Ive driven through like 10 states with fireworks and never had an issue, but I also dont speed and my car doesnt look suspicious. Some guys have horror stories though so YMMV.
Worth checking the Transport section of the forum for state-by-state breakdowns, theres some good threads there.