Conspiracy under Anglo-American law is a wide concept, usually described as an agreement between two or more persons to commit an unlawful act or accomplish a lawful end with unlawful means. Under this law an act which is not a criminal offence if committed by one person may become so if committed by more than one. Therefore the formation of labour unions or political opposition parties may be classified as conspiracy where these are banned. Other kinds of conspiracy include group and organized crime, smuggling, treason, corruption and fraud. Under Anglo-American law two kinds of conspiracy are recognized, 'chain conspiracy' as in organized crime and smuggling where agreement occurs at various levels though individuals may not know their contacts on a certain level; and 'wheel conspiracy' where a number of different people committing the same crime with the same person are held to have conspired, even if they do not know one another. The extent to which charges of conspiracy under this law can be brought, may be unjust and cause confusion. Continental European law (East and West) regarding conspiracy is much more narrowly defined. In most cases conspiracy constitutes a political crime against the state.
Conspiracy under old English law (Edward I, 1305) consisted of an abuse of the processes of criminal justice, malicious and false prosecution. The modern concept of agreement to commit an unlawful act derives from the activities of the Star Chamber in 17th century England, and during the 18th century was applied mainly to labour associations. The American law derives from the 17th century English concept and was also closely connected with labour disputes.