This paper considers the status of laws and legal institutions in modern socio-economic systems, particularly those laws relating to property, contracts and trade. Are such laws mere reflections of other socio-economic relationships between individuals or social classes, or is law itself a part of the underlying socio-economic reality? Albeit in different ways, both Marxists and individualists (in an analytical sense considered here) have typically favoured the idea that law is an epiphenomenon. In contrast, it is argued in this paper that legal relations are partly constitutive of reality. This argument is extended to support Karl Polanyi’s proposition that markets cannot function properly without some intervention by the state.