The Courts of Guernsey are responsible for the administration of justice in the Bailiwick of Guernsey, one of the Channel Islands. They apply the law of the Island, which is a mixture of customary law dating back as far as the 10th century and legislation passed by the legislature, the States of Deliberation. The principal court is the Royal Court and exercises both civil and criminal jurisdiction. Additional courts, such as the Magistrate's Court, which deals with minor criminal matters, and the Court of Appeal, which hears appeals from the Royal Court, have been added to the Island's legal system over the years. It is likely that the oldest law that the Royal Court is called upon to provide judgement over is the Clameur de haro, a Norman form of injunction whereby the aggrieved party makes a plea for justice to Rollo, the 10th century founder of the Duchy of Normandy. (en)