What is "Res Judicata" (既判力) in Japanese Law and How Does It Prevent Re-litigation?

Japanese Attorney at Law - Bengoshi L.L.

• 8 min read

The ultimate aim of civil litigation is to achieve a final and conclusive resolution to a dispute. Once a court has rendered a judgment that becomes "final and binding," it is crucial for legal stability and the conservation of judicial resources that the same matter is not endlessly re-litigated. In Japanese civil procedure, the doctrine that ensures this finality is known as Kihan-ryoku (既判力), often translated as res judicata. This principle dictates that certain determinations made in a final judgment are binding on the parties (and sometimes others) in subsequent lawsuits. Understanding the scope and effect of Kihan-ryoku is essential for businesses to appreciate the conclusiveness of Japanese court decisions and to strategize effectively in litigation.

I. Understanding Res Judicata (Kihan-ryoku) in Japanese Civil Procedure

A. Definition and Core Purpose (Code of Civil Procedure, Art. 114(1))

Kihan-ryoku is the binding effect of a final and binding judgment (kakutei hanketsu 確定判決) which precludes the re-litigation of claims and certain issues already adjudicated between the same parties or their privies. Article 114, Paragraph 1 of Japan's Code of Civil Procedure (Minji Soshō Hō 民事訴訟法) states: "A final and binding judgment shall have res judicata only with regard to the matters contained in the main text of the judgment."

The core purposes of Kihan-ryoku are:

  1. Ensuring Finality of Disputes: To bring an end to litigation by preventing parties from repeatedly suing each other over the same cause of action.
  2. Maintaining Legal Stability and Consistency: To prevent contradictory judgments on the same matter, thereby upholding the authority and consistency of the judiciary.
  3. Promoting Judicial Economy: To conserve the resources of the courts and litigants by avoiding redundant lawsuits.
  4. Protecting Parties from Vexatious Re-litigation: To shield parties who have successfully litigated a matter from being harassed by repeated suits on the same claim.

B. What Constitutes a "Final and Binding Judgment" (Kakutei hanketsu)?
A judgment becomes "final and binding" (kakutei) when it can no longer be challenged through ordinary means of appeal. This typically occurs when:

  • The period for filing an appeal has expired without an appeal being lodged.
  • An appeal is withdrawn or dismissed.
  • The highest court (e.g., the Supreme Court) has rendered a final decision.
    Only such kakutei hanketsu carry the full force of Kihan-ryoku.

II. The Scope of Res Judicata: What, Who, and When?

The preclusive effect of Kihan-ryoku is defined by its three dimensions: objective, subjective, and temporal scope.

A. Objective Scope (Kakkan-teki han'i 客観的範囲): What is Precluded?

This defines what specific matters decided in the prior judgment are binding.

  1. Judgment on the Subject Matter of Litigation (Soshōbutsu 訴訟物):
    • Kihan-ryoku attaches to the court's determination (affirmative or negative) on the existence or non-existence of the right or legal relationship that constituted the "subject matter of litigation" (soshōbutsu) of the prior action.
    • This determination is found in the main text (dispositive part - shubun 主文) of the judgment, which is the operative part containing the court's order or declaration (e.g., "The defendant shall pay the plaintiff JPY X," or "The plaintiff's claim is dismissed").
  2. Extension to Adjudicated Set-Off Defenses (Sōsai no kōben 相殺の抗弁) (Code of Civil Procedure, Art. 114(2)):
    • A significant extension of the objective scope occurs with respect to set-off defenses. If a defendant raises a claim as a set-off against the plaintiff's claim, and the court adjudicates the merits of that set-off claim (i.e., determines whether the claim used for the set-off exists and in what amount), that determination also acquires Kihan-ryoku.
    • This means the validity and amount of the claim used for the set-off cannot be re-litigated in a subsequent action between the parties, up to the amount for which the set-off was asserted.
  3. Generally No Res Judicata for Findings in the Reasoning (Hanketsu riyū 判決理由):
    • As a general rule, the factual findings and legal reasoning (hanketsu riyū) that lead to the conclusion in the main text do not have Kihan-ryoku.
    • This is a key distinction from the concept of "issue preclusion" or "collateral estoppel" as understood in some common law systems, where specific issues actually litigated and decided in the reasoning might be precluded. (The related Japanese concept of sōten-kō or issue preclusion will be discussed later).

B. Subjective Scope (Shukan-teki han'i 主観的範囲): Who is Bound?

This defines which persons or entities are bound by the Kihan-ryoku of the final judgment.

  1. Parties to the Litigation (原告・被告 - Genkoku / Hikoku):
    • Kihan-ryoku primarily binds the actual plaintiff(s) and defendant(s) in the lawsuit where the judgment was rendered.
  2. Universal Successors (Hōkatsu shōkei'nin 包括承継人) (Implicit in Art. 115(1)(1) concept):
    • Individuals or entities who succeed to the entire legal status of a party after the judgment becomes final (e.g., heirs of a deceased party, a company that merges with or acquires a party company).
  3. Specific Exceptions Extending Kihan-ryoku to Certain Third Parties (Code of Civil Procedure, Art. 115, Para. 1):
    Article 115 outlines specific categories of non-parties to whom the effect of Kihan-ryoku extends:
    • Item 1: A person who became a party after the action was initiated (this refers to formal joinder, succession, etc.).
    • Item 2: A person for whom a party to the lawsuit acted as plaintiff or defendant. (e.g., if a trustee litigates on behalf of a beneficiary, the beneficiary may be bound).
    • Item 3: A person who became a successor in interest of a party after the close of oral arguments (kōtō benron shūketsu-go no tokutei shōkei'nin 口頭弁論終結後の特定承継人). This binds those who acquire the specific right or obligation that was the subject matter of the litigation after the factual basis for the judgment was fixed (i.e., after the trial effectively concluded). This prevents parties from circumventing a judgment by transferring the disputed asset or right post-trial.
    • Item 4: A person who possesses the subject matter of the claim for a party or their successor mentioned in the preceding items (mokuteki-butsu o shoji suru mono 目的物を所持する者). This applies, for example, to someone holding a disputed item on behalf of a party bound by the judgment.

C. Temporal Scope (Jiteki han'i 時的範囲): When is the Cut-Off Point for Preclusion?

This defines the point in time with reference to which the judgment's preclusive effect operates.

  1. Standard Time: Close of Oral Arguments in the Fact-Finding Instance (事実審の口頭弁論終結時 - Jijitsushin no kōtō benron shūketsu-ji):
    • Kihan-ryoku reflects the legal situation and the rights and obligations of the parties as they existed at the moment the oral arguments were concluded in the final fact-finding instance of the court that rendered the judgment (this is typically the District Court, or the High Court if it re-examines facts on appeal).
  2. Preclusive Effect on Pre-Cut-Off Issues (The "Blocking Effect" - 遮断効 Shadan-kō):
    • Any claims, defenses, or factual matters that existed before this cut-off time and could have been raised by the parties in the prior litigation concerning the same subject matter are generally precluded from being raised in a subsequent lawsuit. Parties are expected to bring their whole case concerning that subject matter in the initial proceeding.
    • This "blocking effect" or "preclusive effect" prevents parties from "splitting" their claims or defenses related to the same core dispute and litigating them piecemeal.
  3. No Preclusion of Post-Cut-Off Issues:
    • New facts, new evidence of facts that arose after the close of oral arguments in the prior suit, or changes in law occurring after this critical date are not barred by Kihan-ryoku. Such new matters can form the basis of a new lawsuit or a defense in a subsequent action, even if it relates to the same underlying transaction, because they were not part of the legal reality adjudicated in the first judgment.

III. The Effects (Functions) of Res Judicata**

Kihan-ryoku operates in two main ways in subsequent litigation:

A. Negative Effect (Prohibition of Re-litigation - Ichiji fusairi-kō 一事不再理効 or Claim Preclusion)

  • If a subsequent lawsuit is filed between the same parties (or those covered by the subjective scope of Kihan-ryoku) concerning the identical subject matter (soshōbutsu) that has already been definitively adjudicated by a prior final judgment, the subsequent suit is procedurally improper.
  • The court in the second action, upon recognizing the prior final judgment, will typically dismiss the new suit for lacking the "interest to sue" (uttae no rieki nashi 訴えの利益なし) because the matter has already been resolved by Kihan-ryoku. This prevents the same claim from being litigated twice.
  • This is distinct from, but analogous in effect to, the prohibition of parallel litigation of an identical pending case (nijū kiso no kinshi 二重起訴の禁止 - Code of Civil Procedure, Art. 142), which applies before a judgment becomes final.

B. Positive Effect (Binding Effect on Subsequent Courts - 拘束力 Kōsoku-ryoku)

  • If a legal relationship or right that was determined with Kihan-ryoku in a prior action becomes a preliminary or essential prerequisite issue (senketsu mondai 先決問題) in a subsequent, different lawsuit between the same parties (or their privies), the court in the subsequent action is bound by the determination made in the prior judgment.
  • The subsequent court cannot re-examine or make a contradictory finding on that specific point which was the subject matter of the first judgment. The prior judgment is treated as conclusive on that established legal relationship.
    • Example: If Court A definitively rules that a contract between X and Y is valid (subject matter of Suit 1), and then X sues Y in Suit 2 for damages arising from a breach of that same contract, Court B (hearing Suit 2) is bound by Court A's finding of the contract's validity. Y cannot re-argue in Suit 2 that the contract was invalid for reasons that existed at the time of Suit 1.

IV. Res Judicata (Kihan-ryoku) vs. Issue Preclusion (Sōten-kō - 争点効)

  • Issue Preclusion (Sōten-kō 争点効) / Collateral Estoppel: This concept, familiar in common law, generally refers to the preclusive effect of a finding on a specific issue of fact or law that was actually litigated, determined by a final judgment, and was essential to that judgment, even if the subject matter (claim) of the subsequent action is different.
  • Status in Japan: Unlike Kihan-ryoku, which, under Article 114(1), statutorily attaches to the determination of the soshōbutsu (subject matter of litigation) as expressed in the main text of the judgment, a broader doctrine of "issue preclusion" (sōten-kō) that would give binding effect to findings made in the reasoning of the judgment is not as firmly or broadly established as a direct statutory effect in Japan.
  • Limited Recognition Based on Good Faith: However, Japanese courts, in certain limited circumstances, have recognized a preclusive effect similar to issue preclusion, often grounding it in the Principle of Good Faith and Trust (Shingi-soku 信義則). If a specific issue was a central point of contention in a prior lawsuit, was thoroughly litigated by the parties, and was explicitly decided by the court as a necessary step in its reasoning, a party might be precluded from re-arguing that same issue in a subsequent different lawsuit if doing so would be contrary to good faith, fairness, and procedural economy. (See, e.g., Supreme Court, October 26, 1998, Minshu Vol. 52, No. 7, p. 1740, which acknowledged a preclusive effect for certain issues in patent invalidity reasoning under specific conditions). This is a more flexible, judge-made doctrine applied on a case-by-case basis, rather than a rigid rule like statutory Kihan-ryoku.

V. Practical Significance for Businesses

  • Finality and Certainty: Kihan-ryoku is crucial for businesses as it provides certainty. Once a judgment is final, parties can generally rely on it for future business planning and to consider a dispute definitively closed.
  • Preventing Harassing or Duplicative Lawsuits: It protects businesses from being repeatedly sued over the same matter by the same opponent, saving costs and resources.
  • Strategic Litigation Planning: Understanding the scope of Kihan-ryoku is vital when initially framing a lawsuit or defense. Parties must consider what claims and defenses to raise, as matters that could have been litigated concerning the same soshōbutsu might be precluded by the shadan-kō (blocking effect) if not raised.
  • Basis for Enforcement: A final judgment which has Kihan-ryoku is also typically an enforceable title of obligation, allowing the winning party to initiate compulsory execution proceedings if the losing party does not comply.

Conclusion

Res judicata, or Kihan-ryoku, is a fundamental doctrine in Japanese civil procedure designed to ensure the finality of judgments and the stability of legal relations. Its carefully defined objective, subjective, and temporal scopes determine the extent to which a prior judgment precludes re-litigation or binds subsequent courts. For businesses involved in the Japanese legal system, a thorough understanding of Kihan-ryoku is not just academic; it is essential for appreciating the conclusive nature of court decisions, for planning litigation strategy effectively, and for ensuring that once a dispute is resolved, it stays resolved.