From Libertarian Wiki

Slavery is a form of forced labor in which people are considered to be the property of others. Slaves can be held against their will from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to receive compensation (such as wages). Evidence of slavery predates written records, and has existed to varying extents, forms and periods in almost all cultures and continents. In some societies, slavery existed as a legal institution or socio-economic system, but today it is formally outlawed in nearly all countries and condemned by the Universal Declaration of Human Rights. Nevertheless, the practice continues in various forms around the world. Libertarians strongly oppose all forms of slavery.