Laws versus Norms: The Impact of Human Rights Treaties on National Bills of Rights

Many view constitutional incorporation of international human rights treaties as the most effective way to enforce treaty rights domestically. Three competing theories seek to explain why this incorporation occurs or does not occur: (1) states constitutionalize treaty rights because treaties offer authoritative norms that are emulated through the power of their example; (2) states constitutionalize treaty rights because the treaties themselves demand constitutional incorporation; and (3) states only constitutionalize treaty rights when it is in their interest to do so; the treaty does not change state behavior. If the first, norm-based explanation is at work, treaty rights should be emulated widely once a treaty enters into force, regardless of ratification. If the second, law-based explanation is at work, states should constitutionalize their treaty obligations only upon ratification. If the third, interest-based explanation is at work, there should be no independent impact of human rights treaties on constitutional commitments.

This paper examines empirically to what extent eighteen international and regional human rights treaties have altered rights commitments in national constitutions, through either the treaties’ ratification or their mere entry into force. Analyzing 103 constitutional rights in 186 countries over a sixty-one-year period, the paper finds that most treaties do not impact constitutional commitments. There are several exceptions. Two treaties, the CAT and the ECHR, have been emulated everywhere regardless of ratification. Two other treaties changed constitutional commitments among ratifiers only; ratification of the second optional protocol to the ICCPR and the thirteenth optional protocol to the ECHR (both abolishing the death penalty) increase the probability that the ratifying states constitutionally prohibit the death penalty.

The paper also finds that the law-driven impact of human rights treaties is dependent upon the status of international law in the domestic legal system. In dualist systems, where treaties require implementation to have domestic effect, treaty ratification often spurs countries to constitutionally commit to the equivalent treaty rights. In contrast, in countries with a monist system of international law, where international law works directly and automatically in the domestic legal order, ratifying states are less likely to repeat treaty rights in their constitutions. Monist systems are thus characterized by a substitution effect, whereby treaty rights substitute constitutional rights. A similar substitution effect exists within the European and Inter-American regional human rights system, where treaties also work directly in the domestic legal order.