Legal Pluralism and the Problem of Overriding Mandatory Rules
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Author Elaine Obika
Date October 2025
INTRODUCTION
Cross‑border contracting has always operated in the shadow of legal pluralism, but the rise of increasingly complex commercial relationships has sharpened the tension between party autonomy and the mandatory rules of competing jurisdictions. Overriding mandatory rules (hereinafter OMR) sit at the centre of this tension: powerful, unpredictable, and capable of reshaping contractual outcomes regardless of the parties’ intentions. This short analysis examines the disruptive role of OMR in private international law, drawing on contemporary scholarship to illuminate the challenges they pose for legal certainty, harmonisation and the practical realities of international commerce.
Legal pluralism inevitably produces inharmonious outcomes when a single contractual act is exposed to multiple jurisdictions. In the absence of a governing law clause or a specified jurisdiction — or where parties opt out of instruments such as the CISG — the forum will default to its private international law rules to resolve disputes. Unsophisticated parties may fail to include an appropriate choice‑of‑law clause, or their negotiations may be perfunctory, leaving them vulnerable to the application of unfamiliar legal systems. The difficulty is that even where a governing law is chosen, that law may contain overriding mandatory rules (OMR) capable of invalidating contractual provisions partially or entirely, thereby escalating legal costs and undermining commercial expectations. By contrast, sophisticated parties are more likely to anticipate the legal acceptability of clauses across jurisdictions and draft accordingly, reducing the risk of costly surprises.
Lorenzo argues that where a governing law clause exists, the substantive contract law of that jurisdiction should apply supplementarily or interpretatively to preserve party autonomy. Even in the absence of such a clause, he contends that clarification is needed to illuminate the relationship between the substantive contract and conflict‑of‑laws autonomy. In his view, the governing law should be applied restrictively, and only where imperative.
Kim highlights that OMR pose significant challenges across various international contract types, including those governed by German, Swiss and English law. Examples include EU and US trade embargoes, particularly secondary boycotts. The application of third‑state OMR is especially contentious, with no coherent doctrinal solution. Kim further argues that requiring the forum to interpret the laws and cultural norms of multiple states — alongside their OMR — undermines party autonomy, legal certainty and harmonisation.
This suggests that party autonomy is not absolute.
Sources
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[2] Redfern and Hunter Law and Practice of International Commercial Arbitration (Sixth Edition, 2015) para 3.12.
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[7] Rome Convention Article 7.
[8] Rome I Regulations, Article 9(3).
[9] CISG Article 7.
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[13] Min Kyung Kim Comparative Research on the Treatment of Overriding Mandatory Rules of A Third Country (Hart Publishing 2025) pp 96 and 99.
[14] Private International Law Act (PILA) Article 19.
[15] Min Kyung Kim Comparative Research on the Treatment of Overriding Mandatory Rules of A Third Country (Hart Publishing 2025) pp 124-125.
[16] Rome I Regulations Article 9.
[17] Min Kyung Kim Comparative Research on the Treatment of Overriding Mandatory Rules of A Third Country (Hart Publishing 2025) pp 108-109.
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[20] Rome I Article 3.
[21] Rome II Article 14.
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