...Finally, the use of BP substitutes and smokeless powder were only considered by rocketry folks because they, unlike BP, were not specifically regulated by BATFE. That changed in 2013 when the BATFE included black powder substitutes and smokeless powders to the explosives list. BP and its substitutes and smokeless powders by law are not regulated by BATFE if you purchase them for hunting and/or reloading up to a 50 pound quantity. In most states, if you are a hunter or reloader, you can legally purchase any of these propellants without a federal explosive permit, and if you're not a hunter or shooter, in some states you will need to show a BATFE permit/license to purchase them legally....