Over the last 120 years, six international instruments have been created
for the specific purpose of addressing human trafficking. Although these international instruments generally recognize the criminality of trafficking in persons, they consistently failed to explicitly define ‘human trafficking’ as a criminal offense until 2000. Prior to the turn of this century, how can human trafficking as codified under international law be understood? An in-depth legal analysis of these formative international instruments, in combination with their corresponding preparatory documentation, has largely escaped academic scrutiny. This article therefore examines the twentieth century trafficking conventions to fill this gap. It proceeds by identifying and isolating the legal definition of ‘human trafficking’ in each of these early international conventions, extracting the elements contained within, and contextualizing the substance from a criminal justice perspective. This analysis reveals the extent to which the legal construction of ‘human trafficking’ as a crime of international concern has evolved over time and what lessons the Palermo Protocol has or can learn from prior instruments. Reviewing the breadth of international law as it pertains to the traffic of human beings from its legal inception onward enables a greater understanding of this phenomenon.