Abstract: In this comment on Gelbach (JITE 2016), I make two points. First, I support Gelbach’s application of mechanism design (MD) to legal design because it takes information requirements and other constraints seriously. MD derives the best rule under the stated constraints. This rigorously confirms the existing rule’s optimality, reveals a superior alternative, or, if the MD solution appears unrealistic, uncovers additional constraints that any real solution must satisfy. Second, I consider implementing the social optimum, rather than the private optimum. In Gelbach’s discovery example, even a court with limited information can objectively implement some social goals; for other social goals, the court can at least do the best it can according to its subjective beliefs.