There's nothing wrong with voluntary approaches in and of themselves. What we say is that voluntary approaches are never enough, and that's with respect to any human rights front, be it the human rights responsibilities of governments, of individuals, or of companies. We do--and this is from fifty years of human rights research--always come to the conclusion that ultimately you need some sense of obligation and enforcement.
Certainly all sorts of ways in which to encourage voluntary efforts to go further and do more are welcome. Education, training--all of those things are a vital part of it as well, but there's always a necessary role for legislation.