In pursuing their peacekeeping tasks, police are governed by the rule of law which, as we have already noted, is crucial to any liberal democratic order. The time-honored counsel that we should prefer a government “of laws, not men,” reflects the awareness that there is always a potential for tyranny and arbitrariness – a potential that often comes to expression – when social decisions are placed in the hands of individuals who are not governed by rules that also apply to them.

Yet the idea of a rule of law needs more clarification than we have given it so far. Minimally, the rule of law is government by means of firm and pre-announced formal rules, rules that are expressed clearly enough to enable their application to be predicted with reasonable certainty. But rules that fulfill this requirement may still be rules that are oppressive and discriminatory, as they were, for example, in National Socialist Germany and Stalinist Russia. To guard against their oppressive and discriminatory use, laws within a liberal democratic framework must also meet certain normative (including moral) requirements – once catalogued by the legal philosopher Michael Moore as the separation of powers, equality and formal justice, liberty and notice, procedural and substantive fairness, and efficient administration. In other words, laws must conform to broad substantive requirements such as these if the resulting order is to be characterized as one of the rule of law.