You know with the non-ratification of the CTBT treaty, along with a casual reading into Project Plowshare and the other nuclear test treaties leads me to believ

You know with the non-ratification of the CTBT treaty, along with a casual reading into Project Plowshare and the other nuclear test treaties leads me to believe the undertaking of non-military civilian operations utilizing nuclear detonation is still technically legal internationally. And as the detonation of conventional pyrotechnics is legal to be used in the civilian sphere for spectacle and celebration, there is also absolutely nothing legally preventing a nation from incorporating a megaton warhead, into a fireworks display.