The rapid expansion of natural-resource industries in northern Alberta, accompanied by growing environmentalist and aboriginal-rights movements, raises issues of possible extralegal 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 Me´tis people. All except the Me´tis have at various times used some combination of litigation, blockades, occupations, boycotts, sabotage, and violence against economic development projects which they saw as a threat to environmental values or aboriginal 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 characteristics and conflicting political interests.