This article analyses the application of the venire contra factum proprium doctrine by Ukrainian Supreme Court. It explores instances in which elements of the estoppel doctrine have been incorporated into Ukrainian legislation within both public and private law. The study concludes that the Law of Ukraine “On Administrative Procedure” contains a general provision establishing the doctrine of estoppel in the sphere of public law. However, it is noted that, as of now, there is no general legal norm enabling the application of the estoppel doctrine in private law.

The first part of the article examines the normative grounds for applying this doctrine under current legal regulation. The author argues against prioritizing the doctrine of inconsistent behaviour (estoppel) through the lens of good faith over other specific legal norms. The article distinguishes between the application of the principle of good faith and the doctrine of venire contra factum proprium as a derivative of this principle, taking into account the constitutional requirement of the rule of law. It concludes that such application is possible if guided by the Radbruch formula, as recognized in legal scholarship.

Special attention is given to Article 509 of the Civil Code of Ukraine, which mandates the application of the principle of good faith in the context of contractual obligations as a direct legal provision. The article explores the possible consequences of such application, including the invalidation of fraudulent transactions. It also examines the application of the principle of procedural good faith and the consequences of bad faith behaviour under procedural codes.

In the second part, based on case law of the Supreme Court, the article assesses the appropriateness of incorporating the venire contra factum proprium doctrine into the Ukrainian legal system. The author concludes that such incorporation is unfounded, as the existing legal institutions – contract law, pre-contractual relations, transactions, unilateral acts, and renunciation of unilateral acts – adequately address the scenarios in which courts invoke the doctrine of inconsistent conduct.

Bibliography

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