(of the British constitution) discernible rules of conduct that are considered binding by the Crown and those involved in government. They are not laws in the sense of legally binding people in such a way that they could be compelled to perform or be sanctioned for failure to do so in a court. Neither are conventions, strictly speaking, customs because custom is a source of actual law and a convention is not law. It was Dicey who insisted that the constitutional law of the UK could not be understood without understanding the conventions. The nature of conventions as extra-legal was confirmed by the Supreme Court of Canada in Re Amendment of the Constitution of Canada (1981) 125 DLR 3d 1, leading some to believe that the existence of a convention may be a justiciable issue.The bulk of conventions regulate the following: the royal prerogative and the Cabinet; the workings of Parliament, particularly the relationship of the House of Commons and the House of Lords; the organisation of the Commonwealth; the making of war; the dissolution of government; the refusing of the royal assent to Bills; ministers being collectively responsible; the business of the House of Commons being arranged behind the Speaker's chair by the leader of the government and the leader of the opposition; the restriction on the UK Parliament legislating for a former dependent territory now an independent member of the Commonwealth unless it is asked to do so; the appointment of the governor general of an independent Commonwealth country. All involve the conventions.
Collins dictionary of law. W. J. Stewart. 2001.