 The ideal situation for a legal system would be that it be a public system. But in any large society this is not possible. Games are closer to being public systems and most adults playing a game know its rules, or they know that there are judges whose interpretation determines what behavior the game prohibits, requires, etc. Although a game is often a public system, its rules apply only to those playing the game. If a person does not care enough about the game to abide by the rules, she can usually quit. Morality is the one public system that no rational person can quit. The fact that one cannot quit morality means that one can do nothing to escape being legitimately liable to sanction for violating its norms, except by ceasing to be a moral agent. Morality applies to people simply by virtue of their being rational persons who know what morality prohibits, requires, etc., and being able to guide their behavior accordingly.