The psak is regarding the unfortunately all-too common use of explosives (e.g. firecrackers and the various types of rockets) on Purim. The Chief Rabbis said that it is prohibited to use such explosives especially due to the physical dangers involved in using them, and also because it scares people nearby. They even mention the physical danger being so great that one must do whatever he can to get rid of them, and that someone who does use them is chayav b'dinei shomayim.

It is clear from what went on during Purim in my neighborhood that not too many people seemed to care about the physical danger involved nor about the halachic psak of the Chief Rabbis. While in recent years there was a serious decline (locally) in the usage of explosives on Purim, perhaps, at least in part, due to the annual campaign against them run by Ezrat Ahim and Iryat Bet Shemesh, this year I was surprised to hear and see so much explosives being used. I hope there were no injuries, but clearly this year the campaign failed (though I am sure we will hear how successful it was).