Public enforcement of law relies on the use of public agents, such as judges, to follow the law. Are judges motivated only by strategic interests and ideology, as many models posit, rather than a duty to follow the law? We use the random assignment of U.S. Federal judges setting geographically-local precedent to document the causal impact of court decisions in a hierarchical legal system. We examine lower court cases filed before and resolved after higher court decisions and find that lower courts are 29-37% points more likely to rule in the manner of the higher court. The results obtain when the higher court case was decided in the same doctrinal area as the pending case and when the higher court case was decided on the merits. Reversals by the higher court have no significant effects. These results provide clean evidence that judges are motivated to follow the law and are not solely motivated by policy preferences.
IAST working paper, n. 16-55, October 2016