poach on someone's territory
poach on (one's) territory
To encroach on an area of land or part of a market to which someone holds the right or currently controls. The telecoms giant has launched a legal campaign against the new service in an effort to prevent it from poaching on their territory. The indigenous tribe was awarded a huge reparation payment after a federal court agreed that the government had unlawfully poached on their territory for hundreds of years.