Slavery has been practiced as long as human history. Slavery is defined as the status or condition of a person over whom any or all of the powers attaching to the right of ownership are exercised. In early 19th century, states began to abolish slavery in their domestic laws and prohibition of slavery became customary international law around early 20th century. The prohibition of traditional chattel slavery, however, did not guarantee individuals rights to freedom. Contemporary forms of slavery or practice similar to slavery was widespread and this includes serfdom, forced labour, debt bondage, migrant workers, forced prostitution and sexual slavery. Therefore, in 1926, the Slavery Contention was adopted, which was designed to prohibit traditional chattel slavery and various contemporary forms of slavery. Prohibition of slavery has been a direct concern of international community.
Slavery has been regulated by several conventions concerning prohibition of prostitution. Prohibition of prostitution is considered as a effective way to control contemporary forms of slavery. Slavery has been further regulated by ILO conventions, human rights conventions having general characters, and several international conventions and resolutions establishing international criminal tribunals and courts. The development of the prohibition of slavery shows us that the norm was clearly established by customary international law and treaties before the end of World War Ⅱ.
In legal analysis, Comfort Women is a practice similar to slavery and a clear violation of international law prohibiting slavery, and Japan is liable for that.