This article advances debates on the limits of judge-made law to palliate legislative failure to respond to changing practice. Canadian judges have adjusted the general private law to address the situation of unmarried cohabitants. In Kerr v Baranow, the Supreme Court of Canada continued its adaptation of unjust enrichment to this end. The article reports on the first empirical inquiry into how the judgment is operating, including outside the courtroom. Interviews with family lawyers in Quebec show that bringing claims under the adapted doctrine is complex and costly. Variable and unpredictable outcomes impede fair and efficient private ordering. Cohabitation agreements do not seem a satisfactory solution. The study highlights shortcomings in the leading Canadian judgment, which recognizes some cohabiting couples as partnerships but stops short of presuming an equal sharing of gains during the union. But, since the participating lawyers pointed to factors that would reduce the efficacy of reform by judges or by legislatures, the study does not yield a broad preference for legislative reform over judicial reform.