Although slavery and the slave trade has been practiced throughout human history, organized social movements calling for an end to these practices began to gather momentum in the 18th and 19th centuries, particularly in the United States, the United Kingdom and what was then the British Empire.
The legal origins of the banning of slavery date back to the British 1807 Abolition of Slavery Act that abolished, in Great Britain and its colonies around the globe, chattel slavery, whereby people are treated as personal property of an owner and are bought and sold as if they were commodities. In 1863 the United States President Abraham Lincoln issued the Emancipation Proclamation, proclaiming the freedom of 3 million slaves in the ten states that were still in rebellion against the U.S. government.
The League of Nations, created in 1919, was the first international body to address the issue of slavery. In 1924, the League of Nations created the Temporary Slave Commission. The Commission was responsible “for the worldwide exploration and appraisal of the existence of slavery.” After the Commission found slavery to be internationally prevalent, it encouraged the League of Nations to create an international convention focusing on the eradication of slavery.
The Temporary Slave Commission’s recommendations led to the creation of the League of Nations Slavery Convention of 1926. The Convention banned slavery and slave trade and created concrete measures States parties agree to undertake to eliminate slavery and the slave trade in their territories. It serves as the foundation for the prevention and suppression of the slave trade.
Despite its aspirational language, the Slavery Convention failed to establish procedures for reviewing the incidence of slavery in states that are parties to the Convention, and neglected to create an international body that could evaluate and pursue allegations of violations. However, as a summary by the office of the UN High Commissioner for Human Rights notes, the League of Nations was successful in encouraging the implementation of legislation abolishing slavery in countries such as Burma (1928) and Nepal (1926).
In 1934 the League established the Advisory Committee of Experts on Slavery. However its membership was composed of the representatives from the seven European colonial powers – usually retired or former colonial officials. The Advisory Committee’s work was ended by the outbreak of the Second World War.
In 1945, the United Nations was established as the successor of the League of Nations. In 1948, the Universal Declaration of Human Rights stipulated in Article Four that “No one shall be held in slavery or servitude; slavery and the slave trade shall be prohibited in all their forms.”
The post-war political commitment to human rights, as well as movements for national independence in many former colonies contributed to a renewed focus on issues related to slavery.
In 1949 the United Nations Economic and Social Council (ECOSOC) appointed an Ad Hoc Committee of Experts on Slavery to examine the Slavery Convention. They found that there was “not sufficient reason for discarding or amending the definition contained in Article 1 of the Slavery Convention 1926.” However, the Committee did point out that the definition in the Slavery Convention did not cover the full range of practices related to slavery and that there were other equally repugnant forms of servitude that should be prohibited. The Committee therefore recommended that a supplementary convention be drafted to cover practices analogous to slavery.
Consequently, the Slavery Convention was amended by the Protocol Amending the Slavery Convention, done at UN headquarters in New York, on December 7, 1953. The Protocol came into force for Canada the same day. The amendment ensured that the duties and functions created by the 1926 Slavery Convention under the League of Nations are continued by the United Nations.
The Supplementary Convention on the Abolition of Slavery, the Slave Trade, and Institutions and Practices Similar to Slavery, is a 1956 United Nations treaty that builds upon the 1926 Slavery Convention and the ILO Forced Labour Convention of 1930. Article 1 expanded the definition of slavery from one of “chattel slavery” to a definition including a ban of debt bondage, serfdom, servile marriage and child servitude. Similar to the 1926 Slavery Convention slave trafficking, enslavement and giving others into slavery are also prohibited by the Supplementary Convention. The Supplementary Convention entered into force April 30, 1957.
In the years following the Supplementary Convention on the Abolition of Slavery numerous other international documents emerged that confirmed the prohibition of slavery. Article 6.1 of the International Covenant on Economic, Social and Cultural Rights recognized the right to work “which includes the right of everyone to the opportunity to gain his living by work which he freely chooses or accepts.” The International Covenant on Civil and Political Rights guaranteed the protection from slavery, forced servitude or compulsory labour in Article 8. Article 7(2)(c) of the Rome Statute of the International Criminal Court characterizes “enslavement” as a crime against humanity falling within the jurisdiction of the Court.
More recently, the 2000 Protocol to Prevent, Suppress and Punish Trafficking in Persons, Especially Women and Children (the “Trafficking Protocol” developed as a supplementary document to the UN Convention Against Transnational Organized Crime) criminalized trafficking in persons “for the purpose of exploitation” including, “at a minimum, the exploitation of the prostitution of others, or other forms of sexual exploitation, forced labour or services, slavery or practices similar to slavery, servitude or the removal of organs.”
Although appeals have been made for a redefinition of slavery in the context of today’s world, the combined definition set forth in the Convention of 1926 and the Supplementary Convention of 1956 has remained unchanged. The United Nations has made various restatements of the definition, but, according to the UN OHCHR, in the international legal context it has not been altered substantially since 1926.