A central debate in jurisprudence concerns the nature of the judicial obligation in 'hard' cases ones that turn on con- tested points of law. The legal positivists hold that judges have to exercise a discretionary power, not ultimately constrained by law, to decide such cases. Ronald Dworkin has argued that the decision of such cases is determined by law: judges must apply a 'soundest theory' which explains and morally justifies the existing law. Positivists respond that 'wicked' legal systems ones which are the instrument of a repugnant moral ideology are a counterexample to Dworkin. I set out this debate and then evaluate these rival positions in a case study of judicial interpretation in the South African legal system, which is the standard example of a wicked one. I argue that, in the historical and political context of a the South African legal system (Ch.2), the first part of the study (Chs.3,4,5) shows that positivist ideas not only fail to assist judges in a wicked legal system, but make things worse. I argue that the rest of the study (Chs.6,7,) shows how judges do better who adopt the advice that Dworkin gives. I also suggest that their approach can only be stop- ped at the cost of great damage to a legal system and that this should lead us to take seriously ideas put forward by Lon Fuller.