Since time immemorial, states and peoples have entered into formal relationships with each other. Over the ages, traditions have developed on how such relationships are conducted. These are the traditions that make up modern ‘international law’. Like domestic law, international law covers a wide range of subjects such as security, diplomatic relations, trade, culture and human rights, but it differs from domestic legal systems in a number of important ways. In international law there is no single legislature, nor is there a single enforcing institution. Consequently, international law can only be established with the consent of states and is primarily dependent on self-enforcement by the same states. In cases of non-compliance there is no supra-national institution; enforcement can only take place by means of individual or collective actions of other states.

This consent, from which the rules of international law are derived, may be expressed in various ways. The obvious mode is an explicit treaty, imposing obligations on the states parties. Such ‘treaty law’ constitutes a dominant part of modern international law. Besides treaties, other documents and agreements serve as guidelines for the behaviour of states, although they may not be legally binding. Consent may also be inferred from established and consistent practice of states in conducting their relationships with each other. The sources of international law are many and states commit to them to different degrees. The internationally accepted classification of sources of international law is formulated in Article 38 of the Statute of the International Court of Justice. Forming one of the regimes of international law, human rights law has the same source with the former.


a) International conventions, whether general or particular;

b) International custom, as evidence of general practice accepted as law;

c) The general principles of law recognised by civilised nations;

d) Subsidiary means for the determination of rules of law such as judicial

decisions and teachings of the most highly qualified publicists.

These sources will be analysed below.


A. International Conventions


International treaties are contracts signed between states. They are legally binding and impose mutual obligations on the states that are party to any particular treaty (states parties). The main particularity of human rights treaties is that they impose obligations on states about the manner in which they treat all individuals within their jurisdiction.


Even though the sources of international law are not hierarchical, treaties have some degree of primacy. Nowadays, more than forty major international conventions for the protection of human rights have been adopted. International human rights treaties bear various titles, including ‘covenant’, ‘convention’ and ‘protocol’; but what they have in commone are the explicit indication of states parties to be bound by their terms.


Human rights treaties have been adopted at the universal level (within the framework of the United Nations and its specialised agencies, for instance, the ILO and UNESCO) as well as under the auspices of regional organisations, such as the Council of Europe (CoE), the Organisation of American States (OAS) and the African Union (AU) (formerly the Organisation of African Unity (OAU)). These organisations have greatly contributed to the codification of a comprehensive and consistent body of human rights law. 




Human rights had already found expression in the Covenant of the League of Nations, which led, inter alia, to the creation of the International Labour Organisation. At the San Francisco Conference in 1945, held to draft the Charter of the United Nations, a proposal to adopt a ‘Declaration on the Essential Rights of Man’ was put forward but was not examined because it required more detailed consideration than was possible at the time. Nonetheless, the UN Charter clearly  speaks of ‘promoting and encouraging respect for human rights and for fundamental freedoms for all without distinction as to race, sex, language or religion’ (Article 1, para. 3). The idea of promulgating an ‘international bill of rights’ was developed immediately afterwards and led to the adoption in 1948 of the Universal Declaration of Human Rights (UDHR).


The UDHR, adopted by a resolution of the United Nations General Assembly (UNGA), although not a treaty, is the earliest comprehensive human rights instrument adopted by the international community. On the same may that it adopted the Universal Declaration, the UNGA requested the UN Commission on Human Rights to prepare, as a matter of priority, a legally binding human rights convention. Wide differences in economic and social philosophies hampered efforts to achieve agreement on a single instrument, but in 1954 two draft conventions were completed and submitted to the UNGA for consideration. Twelve years later, in 1966, the International Covenant on Economic, Social 21 and Cultural Rights (ICESCR) and the International Covenant on Civil and Political Rights (ICCPR) were adopted, as well as the First Optional Protocol to the ICCPR, which established an individual complaints procedure. Both Covenants and the Optional Protocol entered into force in 1976. A Second Optional Protocol to the ICCPR, on the abolition of the death penalty, was adopted in 1989 and entered into force in 1991.


The ‘International Bill of Human Rights’ consists of the Universal Declaration of Human Rights, the ICESCR, and the ICCPR and its two Optional Protocols. The International Bill of Rights is the basis for numerous conventions and national constitutions.


Besides the International Bill of Human Rights, a number of other instruments have been adopted under the auspices of the UN and other international agencies. They may be divided into three groups:

a) Conventions elaborating on certain rights, inter alia:

  • The Convention on the Prevention and Punishment of the Crime of Genocide (1948)
  • ILO 98 concerning the Right to Organise and to Bargain Collectively (1949)

b) Conventions dealing with certain categories of persons who may need special protection, inter alia:

  • The Convention relating to the Status of Refugees (1951), and the 1967 Protocol thereto
  • The Convention on the Rights of the Child (1989)
  • Optional Protocol to the Convention on the Rights of the Child on the involvement of children in armed conflicts (2000)
  • The International Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families (2000)

c) Conventions seeking to eliminate discrimination

  • ILO 111 concerning Discrimination in respect of Employment and Occupation (1958)
  • UNESCO Convention against Discrimination in Education (1960)
  • The International Convention on the Elimination of All Forms of Racial Discrimination (1965)
  • International Convention on the Suppression and Punishment of the Crime of Apartheid (1973)
  • The Convention on the Elimination of All Forms of Discrimination Against Women (1979) and its Optional Protocol (2000) 


The UN Charter encourages the adoption of regional instruments for the establishment of human rights obligations, many of which have been of crucial importance for the development of international human rights law. The Council of Europe adopted in 1950 the European Convention for the Protection of Human Rights and Fundamental Freedoms, supplemented by the European Social Charter in 1961, the European Convention for the Prevention of Torture and Inhuman or Degrading Treatment or Punishment in 1987, and the Framework Convention on National Minorities in 1994.


The American Convention on Human Rights was adopted in 1969, under the auspices of the Organisation of American States. This Convention has been complemented by two protocols, the 1988 Protocol of San Salvador on Economic, Social, and Cultural Rights and the 1990 Protocol to Abolish the Death Penalty. Other Inter-American Conventions include the Convention to Prevent and Punish Torture (1985), the Convention on the Forced Disappearances of Persons (1994), and the Convention on the Prevention, Punishment and Eradication of Violence against Women   (1995).


In 1981, the Organisation of African Unity, now the African Union, adopted the African Charter on Human and Peoples’ Rights. Two protocols to the Charter have been adopted: the Additional Protocol on the Establishment of the African Court on Human and Peoples’ Rights (1998), and the Protocol on the Rights of Women in Africa    (2003). Other African instruments include the Convention Governing the Specific Aspects of Refugee Problems in Africa (1969), and the African Charter on the Rights and Welfare of the Child (1990).


 B. International custom


Customary international law plays a crucial role in international human rights law. The Statute of the International Court of Justice refers to ‘general practice accepted as law’. In order to become international customary law, the ‘general practice’ needs to represent a broad consensus in terms of content and applicability, deriving from a sense that the practice is obligatory (opinio juris et necessitatis). Customary law is binding on all states (except those that may have objected to it during its formation), whether or not they have ratified any relevant treaty.


One of the important features of customary international law is that customary law may, under certain circumstances, lead to universal jurisdiction or application, so that any national court may hear extra-territorial claims brought under international law. In addition, there also exists a class of customary international law, jus cogens, or peremptory norms of general international law, which are norms accepted and recognised by the international community of states as a whole as norms from which no derogation is permitted. Under the Vienna Convention on the Law of Treaties (VCLT) any treaty which conflicts with a peremptory norm is void.


Many scholars argue that some standards laid down in the Universal Declaration of Human Rights (which in formal terms is only a resolution of the UNGA and as such not legally binding) have become part of customary international law as a result of subsequent practice; therefore they would be binding upon all states. Within the realm of human rights law the distinction between concepts of customary law, treaty law, and general principles of law are often unclear.


The Human Rights Committee in its General Comment 24 (1994) has summed up the rights which can be assumed to belong to this part of international law which is binding on all states, irrespective of whether they have ratified relevant conventions, and to which no reservations are allowed:


[A] State may not reserve the right to engage in slavery, to torture, to subject persons to cruel, inhuman or degrading treatment or punishment, to arbitrarily deprive persons of their lives, to arbitrarily arrest and detain persons, to deny freedom of thought, conscience and religion, to presume a person guilty unless he proves his innocence, to execute pregnant women and children, to permit the advocacy of national, racial or religious hatred, to deny to persons of marriageable age the right to marry, or to deny to minorities the right to enjoy their own culture, profess their own religion, or use their own language. And [...] the right to a fair trial [...].


Although this list is subject to debate and could possibly be extended with other rights not in the field of civil and political rights (for instance, genocide and large parts of the Four Geneva Conventions on International Humanitarian Law), the Committee underlines that there is a set of human rights which de jure are beyond the (politically oriented) debate on the universality of human rights.


 C. General principles of law


In the application of both national and international law, general or guiding principles are used. In international law, they have been defined as ‘logical propositions resulting from judicial reasoning on the basis of existing pieces of international law’. At the international level, general principles of law occupy an important place in case-law regarding human rights. A clear example is the principle of proportionality, which is important for human rights supervisory mechanisms in assessing whether interference with a human right may be justified. Why are general principles used? No legislation is able to provide answers to every question and to every possible situation that arises. Therefore, rules of law or principles that enable decision-makers and members of the executive and judicial branches to decide on the issues before them are needed.


General principles of law play two important roles: on the one hand, they provide guidelines for judges, in particular, in deciding in individual cases; on the other hand, they limit the discretionary power of judges and of members of the executive in their decisions in individual cases.


 D. Subsidiary means for the determination of rules of law


According to Article 38 of the Statute of the International Court of Justice, judicial decisions and the teachings of the most qualified publicists are ‘subsidiary means for the determination of rules of law’. Therefore, they are not, strictly speaking, formal sources, but they are regarded as evidence of the state of the law. As for the judicial decisions, Article 38 of the Statute of the International Court is not confined to international decisions (such as the judgements of the International Court of Justice, the Inter-American Court, the European Court and the future African Court on Human Rights); decisions of national tribunals relating to human rights are also subsidiary sources of law. The writings of scholars contribute to the development and analysis of human rights law. Compared to the formal standard setting of international organs the impact is indirect. Nevertheless, influential contributions have been made by scholars and experts working in human rights fora, for instance, in the UN Sub-Commission on the Promotion and Protection of Human Rights, as well as by highly regarded NGOs, such as Amnesty International and the International Commission of Jurists.