From Envirowiki

The "Law of Limited Competition" is proposed as a universal law (as opposed to a legal law) of ecology, or life, by Daniel Quinn, in his book "Ishmael". The law roughly states that a predator may compete to it's best ability, but it may not go beyond that - it may not reduce the natural ability of it's competitors to compete. The outcome of the law is enhancement of diversity.

The first example given in Ishmael is that of hyenas given the option to kill off lions (a competitor). In nature, this doesn't happen, however, if it did, the lack of lions would mean an expansion in the gazelle population, which in turn would allow for a greater population of hyenas, and, if the law continued to be broken, would reduce the entire ecosystem to a homogenised cycle of hyena < gazelle < grass < hyena.

Quinn argues that humans are the only species to have broken this law, beginning with agriculture (and removing the competition of the products thereof, ie. grazing species from "our" grain fields, carnivores from "our" meat animals) and that we have a cultural myth that keeps us from realising this.