This article problematizes the persistence of sexual inequality in Britain, by examining the intellectual work performed by judges as they sought to preserve men’s paternal rights from new challenges in the nineteenth-century. One set of challenges included changing understandings of childhood and male domestic authority, another derived from the peculiarities of British state formation. The article argues that the gender order was repeatedly unsettled by two processes of state formation: first, the efforts of reformers to rationalise the multiplicity of jurisdictions that characterised the ancien regime; second, the process of bringing within one polity the separate bodies of law found in England and Wales, Scotland and Ireland. Judicial efforts to reconfigure paternal rights in the face of these challenges produced a more severely patriarchal model of paternal rights than had existed before, but this proved short-lived. At the end of the nineteenth century, conflicts within the legal elite unravelled this patriarchal settlement in favour of a new model, which endured until the 1970s. This body of law was still profoundly inegalitarian, but used a more expansive definition of child welfare to place new limits on paternal power. Exploring this story reveals the extent to which the fragmentation of the juridical state created a double standard between rich and poor, with the rights of rich fathers enjoying much greater legal protection than those of the poor. The article argues that we should not see the law as a stable patriarchal monolith but as a gendered system that was continuously being reconstructed at the point of use by actors with considerable freedom of manoeuvre. Any history of the law must therefore also be a history of judicial mentalities.