Were Native Americans justified in leaving reservations and refusing further relocations from the US government?

Even US President Grant said that the Native American tribes were correct in resisting the "reservation system". He did, however, need to help expand US western growth. His orders to his generals in the West were to force Native Americans on to reservations. He believed this was a must in order to expand settlements and create farmlands and mines. Grant had no choice despite his ideas to avoid conflicts.