In private international law, the public policy doctrine or ordre public (French: lit. "public order") concerns the body of principles that underpin the operation of legal systems in each state. This addresses the social, moral and economic values that tie a society together: values that vary in different cultures and change over time. Law regulates behaviour either to reinforce existing social expectations or to encourage constructive change, and laws are most likely to be effective when they are consistent with the most generally accepted societal norms and reflect the collective morality of the society.
In performing this function, Cappalli has suggested that the critical values of any legal system include impartiality, neutrality, certainty, equality, openness, flexibility, and growth. This assumes that a state's courts function as dispute resolution systems, which avoid the violence that often otherwise accompanies private resolution of disputes. That is, citizens have to be encouraged to use the court system to resolve their disputes. The more certain and predictable the outcome of a court action, the less incentive there is to go to court where a loss is probable. But certainty must be subject to the needs of individual justice, hence the development of equity.