Forty-two states and the District of Columbia permit the use of fireworks through federal regulation. So as long as this drone isn't in Delaware, New York, Massachusetts, New Jersey, Illinois, Iowa, Ohio, or Vermont, the pilots should be in the clear legally. A few states have tried to pass laws that forbid arming drones, which might apply to a firework-toting quadcopter. Wisconsin and North Carolina both outright ban weaponized drones, and Arkansas, California, Connecticut, and Massachusetts have all considered such measures. Even without explicit legal prohibition, it's still best to limit drone roman candle fights to willing participants, far away from important buildings.