On the other hand, one could also say that it would also be consistent with neo-liberal principles to have simply let slavery whither under the principles of the free market, as the "Yes Men" argue in their guise as members of the WTO (or, in more accurate terms, that slavery was really only ever formally outlawed anyway):
The whole segment: http://www.youtube.com/watch?v=Eo-1W_8otS4
The two minute excerpt especially relevant to slavery: http://video.google.com/videoplay?docid=-5206347030584294754#
-s