Suppose P1—whether buyer or seller—feels dissatisfied with M1's services, say, because he believes that M1 is favoring P2's interests over his own. Suppose further that no complaint on the part of P1 has had any effect on M1. Three outcomes are then possible. First, if no other mafioso (or state) is available (at least none of comparable strength)—in other words, if M1 has a monopoly on protection—the situation is straightforward: P1 has no alternative because no one else is able to help him. (One condition for supplying credible protection is that P1 and P2, both individually and together, must be weaker than M1; otherwise P1 could take the matter into his own hands.) Suppose, by contrast, that there is competition in the market: another mafia firm (M2), wielding power comparable to that of M1, supplies protection. In this case P1 has the option of enlisting M2's protection against M1. This brings us to the two remaining possibilities: M2 faces a choice between intervening in favor of P1 (ultimately risking a war with M1) or abstaining from intervention altogether.

Diego Gambetta, The Sicilian Mafia The Busi…, loc. 183