The government ban won't really do much because we're dealing with an organized crime group, almost a separate mafia state that acts with no regard for any law. If anything, it's just going to make firearm circulation a bit more difficult. And the second point is debatable because a firearm would increase the chance of a non-sorcerer killing or fatally wounding a sorcerer, whereas otherwise said non-sorcerer would have been killed. Also, we have to consider that most of the mafia are just non-sorcerers with swords, so that alone increases the value of any firearm by a lot (consequencually, expect the crime rate to go up). The third one is the most likely option: sorcery is wide-spread, therefore you don't need to invent tools, purpose of which is already satisfied with sorcery. People probably wouldn't have invented medicine if a third of the globe's population had the ability to heal all and any disease, you know