The rapid expansion of natural-resource industries in northern Alberta, accompanied by growing environmentalist and aboriginal-rights movements, raises issues of possible extra-legal and even violent resistance to industrial development. Five potential sources of opposition can be identified: individual saboteurs, eco-terrorists, mainstream environmentalists, First Nations, and the Metis people. All except the Metis have at various times used some combination of litigation, bocycotts, sabotage, and blockades, occupations, and violence against economic development projects which they saw a threat to environmental values and aborginal rights. Such incidents will probably continue in the future, as they have in the past. However, extra-legal obstruction is unlikely to become large-scale and widespread unless these various groups make common cause and cooperate with each other. Such cooperation has not happened in the past and seems unlikely in the future because the groups have different social characteristis and conflicting political interests.