 He was chiefly responsible for the "Indian New Deal", especially the Indian Reorganization Act of 1934, through which he intended to reverse a long-standing policy of cultural assimilation of Native Americans.Collier was instrumental in ending the loss of reservations lands held by Indians, and in enabling many tribal nations to re-institute self-government and preserve their traditional culture.Some Indian tribes rejected what they thought was unwarranted outside interference with their own political systems that the new approach had brought them.