Law is a set of rules which governs human behaviour and provides a framework to ensure a peaceful society. It can be enforced by mechanisms such as police and courts, and punishments can be imposed when people break the laws. Law shapes politics, economics, history and society in a huge variety of ways.
Law covers a wide range of activities, from regulating contracts and property to defining the limits of censorship and the responsibilities of the military and police. The rules of law are derived from a number of different sources, including legislation and precedent. Some countries, like the United States, have a common law system, which relies on judicial decisions in cases rather than statutes. These are combined into a body of case law, which judges use to judge new cases. Other countries have a legislative system with statutes and a supreme authority. This system tends to be more formally written, but may also be influenced by constitutions and the rights encoded in them.
Often, however, the legal system is based on religious precepts, such as Jewish Halakha and Islamic Sharia. These act as a basis for law, which judges and governments then further elaborate using Qiyas (interpretation and reasoning by analogy), Ijma (consensus) and precedent. These are then applied to specific situations and circumstances. This enables the laws to be made applicable to a wider variety of people and situations than would otherwise be possible, without the need for a lengthy process of deliberation or consensus.