Do we have a moral duty to obey the law? Do we, in other words, have a moral obligation to comply with legal rules simply because they are legal rules? What about obviously unfair or unjust laws? Or laws that impose unreasonable demands on us? The question of whether we have a duty to follow the demands of the law raises some fundamental issues regarding the nature of law and its moral claims. This chapter examines a number of possible reasons for obeying the law. It will examine the principal justifications for obedience: fair play, consent, the common good, and gratitude.