How did Ronald Dworkin argue that moral reasoning matters in difficult constitutional cases?

Ronald Dworkin argued that moral reasoning is essential for resolving difficult constitutional cases because he believed that the law is not merely a collection of source-based norms, such as statutes or prior court rulings. Instead, he proposed that the law is defined by the best "constructive interpretation" of those norms.1

In Dworkin’s view, a constructive interpretation seeks to explain existing legal sources through the lens of fundamental moral principles, such as fairness and justice. By applying these principles, judges can provide an attractive moral justification for the legal system as it currently exists. This process aims to achieve "principled coherence" between a current decision and past legal precedents, ensuring that the law remains consistent with the moral values that underpin it. While critics, including legal positivists, argued that such moral considerations are not necessarily part of the law unless explicitly recognized by society, Dworkin maintained that these moral dimensions are intrinsic to determining what the law actually is in complex scenarios.1