Cognitive scientists and others who do research on analogical reasoning often claim that the use of precedent in law is an application of reasoning by analogy. In fact, however, law’s principle of precedent is quite different. The typical use of analogy, including the use of analogies to earlier decisions in legal argument, involves the selection of an analog from multiple candidates in order to help make the best decision now. But the legal principle of precedent requires that a prior decision be treated as binding, even if the current decision-maker disagrees with that decision. When the identity between a prior decision and the current question is obvious and inescapable, precedent thus imposes a constraint quite different from the effect of a typical argument by analogy. The importance of drawing this distinction is not so much in showing that a common claim in the psychological and cognitive science literature is mistaken, but that the possibility of making decisions under the constraints of binding precedent is itself an important form of decision-making that deserves to be researched in its own right.
Schauer, Frederick. "Why Precedent in Law (and Elsewhere) is Not Totally (or Even Substantially) About Analogy." KSG Faculty Research Working Paper Series RWP07-036, August 2007.