For obvious reasons, when dealing with explosives, fireworks or other pyrotechnics, it is extremely important to be aware of any applicable laws, rules or regulations. People (especially law enforcement officers) don't usually have much of a sense of humor about these things; so it's best to dot all the i's and cross all the t's.
Founding Documents (High Resolution Images)
Federal Explosives Law
Washington State Explosives Law
Washington State Fireworks Law
Coming soon: More links to relevant state and local laws...