That system that Chief Joseph is talking about is Indian reservations.
Indian reservations were areas designated by the government for the resettlement of Indigenous people. This usually meant that more desirable areas were taken from the indigenous population to be used by white settlers, whereas the population was relocated to less desirable land. Chief Joseph, the leader of a band of Nez Perce refused this relocation and was pursued by the government during the Nez Perce War. He despised the reservation system, and he argued that the Indigenous people that were relocated would never thrive. He claimed that humans need liberty of movement in order to feel happy and have a good life.