Despite some differences in family law systems concerning affiliation laws, most Western European legal systems are historically interconnected and have common legal provisions for the establishment of legal paternity, such as the application of the Roman law rule of the presumption of paternity – Pater est quem nuptiae demonstrate – which legally ties men to any children born to their wives. Even if there is no biological tie between the child and the mother’s husband, the law considers that the husband is the legal father and in most countries it is necessary to take civil proceeding in order to remove that presumption of paternity. As such, marriage retains a privileged place as the preferred way of attributing paternity. In relation to children born outside legal marriage if the unmarried father voluntarily registers the child’s birth with the mother, in some countries, such as Portugal, he will automatically be recognised as the legal father. But when that does not occur and the birth certificate does not indicate the identity of the child’s father, efforts may be made to establish fatherhood via court proceedings.