Had the abolitionists of the past, the likes of Abraham Lincoln or William Wilberforce, been able to see into the twenty-first century, what might have struck them as very strange was that while they had come far in ending slavery and suppressing human exploitation, they seemed to have lost sight of what the term "slavery" means. This, despite the fact that for more than eighty-five years there has been a consensus in international law as to the legal definition of slavery. In the case of slavery the element of possession is fundamental. It allows people to drain the swamp and leave the definitional quagmire which has marginalised the legal definition of slavery. With the legal definition of slavery marginalised, people looked elsewhere to define slavery. A survey of the academic literature on contemporary slavery -- including much of the legal literature on the subject -- would show that, in the main, it has turned to the work of Kevin Bales and his sociological reading of what constitutes slavery.
Allain, J., & Bales, K. (2012). Slavery and its definition. Global Dialogue, 14(2), 6-14