  Legal rights and obligations vary when certain institutional and other nonmoral social facts vary; and cannot vary as long as such facts remain the same. The class of relevant facts most prominently includes institutional practice, the actions or practices of political institutions and ultimately the actions and psychology of the agents that operate within such institutions. You came to have the right to have the defective phone replaced or repaired by the seller and under the conditions mentioned when certain facts of this kind obtained: most directly, when the European Parliament and the Council of the EU adopted a certain Directive and the UK Parliament adapted its own legislation to give effect to it. You did’t have that specific right under the specific conditions before these actions were taken, and there is no guarantee you will retain the right now that the UK has completed its withdrawal from the EU and may take unilateral action to modify or abolish it. You couldn’t have come to have the right or, once you did, to lose it, unless some facts of that character obtained. Your right is therefore contingent upon and varies with the actions and practices of political institutions. The task for theories of law is to offer an account of legal rights and obligations that explains these relations. Legal positivism is an account of legal rights and obligations that appeals, at the fundamental level, exclusively to institutional and other nonmoral social considerations. Interpretivism is a kind of natural law or “nonpositivist” theory since it claims that, in addition to institutional practice (and perhaps other nonmoral social factors), certain moral facts necessarily play some role in the explanation. It makes a number of related distinctive claims within that approach.