Reports are that the bombers bought fireworks and harvested the black powder from them. Are we going to put taggants in bottle rockets now? Background check and 7 day waiting period for sparklers?
Moreover, the powder in just about all fireworks isn’t ‘black powder’, but ‘flash powder’ like magicians use. When it burns, it burns bright white. This doesn’t explain how the bombs they detonated at the Boston Marathon had a yellow detonation flame rather than bright white as expected when using flash powder.
Fireworks nerds have been talking about this at length on Internet forums dedicated to fireworks hobbyists and professional pyrotechnics showmen ever since the bombing investigators claimed that the terrorists bought mortar packs with lifting charges at a fireworks wholesaler in New Hampshire, reportedly the same place the 2010 Times Square bomber used to purchase a large amount of ‘M-88’ firecrackers for his bomb which failed.