Immigration Law: the branch of a country’s legal system wherein legislation, custom and court precedent combine to define the ways in which that country’s nationality and citizenship are transmitted, acquired or lost. Today, nationality law is based either on jus soli or jus sanguinis, or on a combination of the two. Jus soli is the principle in which a child born in a country’s territorial jurisdiction acquires that country’s nationality. In jus sanguinis, either the father or mother must normally be a citizen of the country in question in order for the child to be a citizen.