Norm Change in the Common Law

An account of legal change in a common law system is developed. Legal 1 change takes place incrementally through court decisions that are constrained by 2 previous decisions in other courts. The assumption is that a court’s decision has to 3 be consistent with the rules set out in earlier court decisions. However, the court is 4 allowed to make add new distinctions and therefore make a different decision based 5 on factors not present in the previous decision. Two formal models of this process 6 are presented. The first model is based on refinement of (the set of factors taken into 7 account in) the set of previous cases on which a decision is based. In the second 8 model the focus is on a preference ordering on reasons. The court is allowed to 9 supplement, but not to revise the preference ordering on reasons that can be inferred 10 from previous cases. The two accounts turn out to be equivalent. A court can make a 11 consistent decision even if the case base is not consistent; the important requirement 12 is that no new inconsistencies should be added to the case base. 13 AQ1