An Analysis of the Unilateral Promise to Perform a Natural Obligation Considering the 2016 Amendments to the French Civil Code

Document Type : Research Paper

Authors

1 Associate Professor of Private Law,The Faculty of Law and Political Science, Ferdowsi University of Mashhad, Mashhad, Iran.

2 PhD Candidate in Private Law, The Faculty of Law and Political Science, Ferdowsi University of Mashhad, Mashhad, Iran.

10.22059/jlq.2026.403510.1008036

Abstract

Introduction
Natural obligation in contract law is an institution in which a person feels a moral duty toward another, but this obligation is not recognized by law and therefore does not carry a legal claim or be enforced by civil action. Natural obligation is a traditional and still controversial concept in private law; recent reforms to the French Civil Code have partly addressed it. Natural obligation is not comprehensively defined in the Iranian Civil Code, and the law addresses only one of its effects; hence, the concept and nature of natural obligation remain an important challenge in Iran’s legal system. In practice, a natural obligation may fall within the sphere of civil law and become non-recoverable through a promise or voluntary payment. Article 266 of the Iranian Civil Code does not address how to convert a natural obligation into a civil obligation, which raises doubts about the validity of a unilateral promise of a natural obligation. Notably, unlike Iranian law, French law—pursuant to Article 1100 of the Civil Code—considers the promise to perform a moral obligation as a new source of obligations. The 2016 reforms of French law brought law and ethics closer at the point of natural obligations and elevated the unilateral promise to perform a natural obligation from an obscure, obsolete institution to one with a clear and coherent legal function. In that system, the source of enforceability for the unilateral promise to perform a moral obligation is not merely subsequent material performance, but the promise itself, which, once realized under the necessary conditions, becomes enforceable. There, the promise serves as a link between ethics and law by operating within the domain of non‑enforceable obligations (moral or conscience‑based obligations, time‑barred debts, and the like). Under general contract rules, a unilateral promise does not create any obligation, but the question is under what conditions a promise to perform a moral obligation produces the desired legal effects. Accordingly, the principal question of this study is: what are the necessary conditions for the validity of a unilateral promise to perform a natural obligation, and what effects does it produce? This paper aims to identify the conditions required for a promise to create a legal obligation from a natural obligation, and to examine its effects. It argues that a unilateral promise to perform a natural obligation, provided that conditions such as the intention to be legally bound, conformity with public order and good morals, and free will are met, may be recognized as a source of enforceable legal obligations and as a starting point for respecting legitimate expectations in society.
Method
The research uses a descriptive‑analytical method, reporting and describing data relevant to the study and analyzing the subject in light of the Iranian legal situation. Given the long tradition of the subject in French law and its recent statutory reform, a comparative examination of French law, with an emphasis on its modern legislative amendments, has been conducted.
Conclusions
This study, by reviewing Iran's legal status and comparing it with the French legal system, considers a unilateral promise to perform a natural obligation, subject to certain conditions, as a source of enforceable obligations. Likewise, as the French Civil Code, in Articles 1301‑1 and 1302‑2, distinguishes between civil and natural obligations and applies the principle of non‑recoverability to delineate a relatively precise scope for the performance of natural obligations, the Iranian legislator should amend Article 266 of the Civil Code to expressly regulate the formation and effects of natural obligations with regard to promissory performance. The phrase “at the debtor’s discretion” in Article 266 indicates the need to recognize the prior existence of a natural debt and the sense of obligation toward it, and it manifests the necessity for the debtor’s knowledge and awareness of the nature of the debt. Until statutory reform and new rules are adopted, a desirable interpretation should be drawn from the traditional provisions to mitigate existing challenges as much as possible. Moreover, by a broader interpretation of the term “performance,” the conversion of a natural obligation into a legal obligation need not be limited to payment of the debt; payment is merely the predominant mode, and a promise to perform should stand alongside it.

Keywords

References

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Law Quarterly
Volume 56, Issue 1
May 2026
Pages 61-86

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