All over the common law world complaints are heard about the manner in which the courts decide the living arrangements for children when their parents separate. A large body of contributions from scholars and commentators from various disciplines exist, and are still being contributed, that highlights problems, critique outcomes, and make recommendations relating to these types of legal decisions. Will their work make a difference to legal outcomes and, if so, why? This thesis uses the socio-legal theory of Niklas Luhmann to show that it is because of how the legal system operates that the expectations of parents, scholars and interest groups, will invariably be disappointment and that ultimately what is required for these types of decisions, cannot be achieved by the legal system. Luhmann argued that the legal system operates in a closed, self-referential manner to produce its own messages as regards the values of legal and illegal. This manner of functioning is called autopoiesis. By its operations the system self-selects and simplifies information generated outside of the system in a manner that will stabilise normative expectations, which is all that the law does. Normative expectations are created with society in mind and not individuals. This challenges the individualistic approach that is required in custody and contact decisions after parental separation. The research starts at the historical point when the common law legal system gained jurisdiction over children. The research follows the development of the ‘welfare principle’ upon which custody decisions are based and illustrates the relevance and application of Luhmann’s theory. This study investigates the limitations of the legal system to make decisions about children’s welfare and best interests in the context of custody and contact decisions.