Recent reports from the United Nations International Children’s Emergency Fund (UNICEF) highlight a global decline in child marriage. Yet the practice still persists, impacting 640 million girls and women in the last decade. This blog considers how, despite the lack of a clear basis in treaty law, state practice seems to be moving toward a minimum legal age of 18 for marriage.

An Elusive Consensus

Despite the clear stance of UNICEF and the Office of the UN High Commissioner for Human Rights (OHCHR) – which defined child marriage as “any marriage where at least one of the parties is under 18 years of age” – states have historically failed to adopt a clear legal standard. From early 1950s to late 1980s, the drafters of six consecutive treaties failed to agree on a specific minimum age for marriage opting instead to leave this matter to the discretion of individual states. Thus, neither the 1956 Supplementary Convention to the Slavery Convention; the 1962 Convention on the Consent to Marriage; the 1966 International Covenant on Civil and Political Rights; the International Covenant on Economic, Social and Cultural Rights; the 1979 Convention on the Elimination Discrimination Against Women (CEDAW); or the 1989 Convention on the Rights of the Child (CRC) explicitly prohibit child marriage.

While the Supplementary Convention (Article 2), Consent Convention (Article 2), and the CEDAW (Article 16(2)) require that parties establish a minimum age for marriage, they stop short of specifying what that age should be. Consequently, states have the discretion to set their own minimum. Only the CRC clearly defines what constitutes a “child” (Article 1), yet the drafter failed to reach consensus and provisions on marriage were removed during the negotiations. As a result, the CRC contains no provision on marriage.

Harmonious Treaty Interpretation

The principle of “systemic integration”, part of customary international law and reflected in Article 31(3)(c) of the Vienna Convention on the Law of Treaties (VCLT), requires the above treaties to be read together. In 1994, the CEDAW Committee did just that, stating that the CRC “preclude[s] States parties from permitting or giving validity to a marriage between persons who have not attained their majority,” adding that it “considers that the minimum age for marriage should be 18 years” [36]. Although various treaty bodies and a significant portion of both academic and grey literature have long supported this standard, it is only recently that it has begun be reflected in state practice.

State Practice and Treaty Interpretation

When interpreting a treaty, Article 31(3)(a) and (b) of the VCLT mandates that “any subsequent agreement” among the parties, as well as “any subsequent practice” in the treaty’s application, must be taken into account. The practices of human rights treaties bodies may be considered to be both subsequent agreement or subsequent practice. That said, the legal status of such practice is dependent on states’ consent.

The CEDAW and CRC Committees’ joint recommendation from 2014 called for 18 as the minimum age, albeit with exceptions. This exception was removed in a recommendation from 2019, suggesting 18 as the absolute minimum age for marriage. Despite limited support in state practice before 2015, the number of states with an absolute ban on marriage under the age of 18 has since grown from 17 to 45. This still means that approximately three times as many states still allow marriage under the age of 18, though typically only under exceptional conditions. Thus, while most states cannot be said to have consented to the 2019 recommendation, most do seem to support its predecessor.

A Potential Universal Standard by 2030

The recent trends in state practice, coupled with the unanimously adopted UN Sustainable Development Goals – specifically, the objective to eliminate child marriage by 2030 – may indicate a growing acceptance for 18 as the minimum age for marriage, although still subject to exceptions. Despite years of futile negotiations, an international minimum standard is therefore gaining momentum, potentially becoming a universal standard by 2030. In essence, the standard of 18 is coming of age.