The Effect of Marriage on Nationality: A Comparative Study Between Nigeria and Iran

Marriage, as a social institution with inevitable legal consequences, brings about legal effects within any legal system and has historically constituted a primary source of conflict of laws in Private International Law. This article examines the issues arising from these effects comparatively, aiming to elucidate how familial interactions, specifically marriage, influence questions of nationality, among which dual citizenship is a well-known phenomenon. In Nigeria, marriage is not strictly codified; the domestic legal order officially recognizes three distinct types: customary, Islamic (Shariah), and statutory marriages, each governed by its own legal regime. Internationally, however, the Nigerian government only recognizes only the statutory marriage, by virtue of its formal registration. As a result, marriages contracted under customary or Shariah law are more vulnerable to legal issues on the international stage. These issues have prompted many couples in Nigeria to opt for the so-called “double-decker marriage,” a combination of two marriages: a customary or shariah marriage along with a statutory marriage, mainly to reduce international legal complications by securing a state-issued marriage certificate. In Iran, by contrast, the legal landscape is markedly distinct. The State recognizes only one form of marriage: statutory marriage. Iran maintains a stricter stance on nationality issues, ensuring that public order, legislative intervention when needed, and state prerogative are consistently upheld. Everyone in the country, regardless of religion, sect, or custom, must follow this one mode of marriage. Notably, failure to register a “permanent marriage” (nikah da'im) in Iran is a criminal offense punishable by law. A noteworthy commonality between the two jurisdictions is the influence of Shari’ah law, although each follows a distinct school of Islamic jurisprudence (madhhab). In family law, especially marriage, the legal schools of both nations share many similarities.