Virtually all political persuasions agree on the need for police. For libertarians, maintaining a criminal justice system, of which the police are a major component, is viewed as one of the few legitimate roles of government.

The first modern and professional police force was the London Metropolitan Police Service, established in 1829. There had been substantial public opposition to a large and possibly armed police force until then, based on fears it could be used to suppress protest or support unpopular rule. The example of France, which had secret police at the time, was significant.