IMPLEMENTING A POLICY
Erie Railroad v. Tompkins is of much broader significance than most precedent-forming decisions. If, for example, the highest court in a particular jurisdiction has decided that under given circumstances a motorist exercises a reasonable degree of prudence when he decreases his speed to twenty miles an hour while approaching and crossing a railroad track, this is the law. All courts of the jurisdiction are bound to follow this precedent. They may have difficulty in discovering whether subsequent cases actually occurred under substantially similar circumstances or whether later drivers really took the required care, but once these questions of fact have been established, there is no difficulty in administering the principle of law. A precedent in the field of contract law is normally of equal simplicity. A court of last resort has determined that certain acts on the part of an offeror followed by another set of actions performed by an offeree produces a binding contract. It may not be easy to evaluate the conflicting stories of opposing sides in a dispute; but once this has been done, it is seldom difficult to apply the precedents so as to discover the appropriate legal solution of the case.
Of course, when an appellate court decides to change the law, it is faced with a question of policy: Are motorists who drive across railroad tracks at twenty miles an hour taking sufficient precautions to safeguard themselves and other people? Should a man be allowed to wait three weeks before accepting an offer without losing the right to accept? These are important problems for the protection of personal and property rights, and their solution may be difficult. However, once the highest court of a jurisdiction has written the change into precedent, inferior tribunals have little discretion whether or not to apply a rule of substantive law. The policy has been made for them and the tasks which remain are largely routine.