Review of res judicata in administrative court judgment

Abstract

          The concept of res judicata in judgments is critically important to the legal system, as it serves as a mechanism to bring disputes to a final resolution, preventing endless litigation. Once the legal system deems a judgment final and not subject to further contestation, that judgment becomes binding, regardless of whether it is deemed fair or correct. This article explores the origins of the concept of res judicata in Roman law through the explanations of Friedrich Carl von Savigny, which led to the integration of this concept into the principle of legal certainty under the rule of law.

          However, there was a debate about whether the effect of res judicata applies only to the procedural aspects of a case in subsequent proceedings, or if it also impacts the alteration of rights, duties, or statutory laws. It is now generally accepted that the effect of res judicata is limited to procedural matters within the court’s jurisdiction, without changing substantive law.

          Although it is clear that a final judgment affects only procedural matters in future cases, it remains a topic for further consideration whether the binding effect of res judicata extends beyond the issues the court has ruled on, to include other statements or facts affirmed in the judgment. The study found that a judgment with res judicata effect binds the court in future cases only on the issues the court has decided. Other components of the judgment that do not address the disputed issues may be used to interpret the binding effect of the judgment. However, the reasoning in the judgment, especially the application of law by the court, although not binding in itself, is closely related to the issues decided by the court. Thus, it can be considered as having res judicata effect alongside the decision on those issues. This principle is also confirmed by the Thai legal system, which upholds the res judicata effect of judgments on issues the administrative court has ruled upon, as stipulated in Articles 96 and 97 of the Rule of the General Assembly of Judges of the Supreme Administrative Court on Administrative Court Procedure, B.E. 2543.

          Furthermore, the study found that the binding effect of res judicata also applies to courts of different systems. Once an administrative court has rendered a final judgment, it binds the judiciary to apply the issues already adjudicated by the administrative court to their own cases. This finding contributes to the harmonization of judgments between administrative and judicial courts, reinforcing the coherence of the dual-court system.