I wouldn't necessarily say with impunity, because it all caught up with them eventually. The reason the Mafia isn't killing like that anymore, especially members of the State, is because they're working on becoming one with the State again. Their weapons today are infiltration and subversion of the political and business spheres rather than bullets and bombs. I'm really amazed at how Cosa Nostra really has a grip on the island's underworld and everyone listens to whoever it is in charge. There's rarely ever a Mafia killing in Sicily anymore, unlike other Italian regions like Puglia, Campania, and Calabria.
yes, their main target nowadays is the infiltration of politcs/institutions and legit economy minimizing the number of homicides; Cosa Nostra has still a hierarchical structure that's why it kills less than other organizations that have a horizontal one, like the Camorra
