Administrative agencies play a substantial role in the formulation and implementation of national policy. Central to this role is their exercise of discretion. A normative consensus exists that such discretion should be constrained by administrative deference to the rule of law. The courts of appeals are expected to insure that such discretion is constrained. The analysis reported below examines how effectively they fulfill that expectation. The findings suggest that agency success is related to political considerations, with agencies being successful when their decisions are consistent with the policy preferences of the judges. However, variables that captured elements of the legal model were also related to success. Taken together, it appears that the appeals courts respond to both legal concerns and political preferences. Thus, the courts appear to fulfill the expectation that they will constrain the worst abuses of discretion by imposing the rule of law.