I mentioned my evolving views on the subject of legalizing prostitution a little while ago, my main misgiving being that legalization does not appear (at least in the cases examined) to do a great deal towards preventing human trafficking, and in fact may make it worse.
This recent series on the subject of human trafficking by WGBH is well worth your time. I listened to the last installment this morning, that summarized what can be done to combat this problem. I found some of their recommendations more satisfying than others, but most glaring to me was the policy recommendation that they didn't make, at least not explicitly:
Blanket, permanent immigration amnesty for suspected victims of human trafficking.
And yes, I do mean "suspected"--more specifically, that the crime of trafficking need not be "proven" in a legal sense (that no one need be convicted for it) for the victims to qualify for amnesty.
One of the greatest weapons traffickers have against their victims in the US is fear of running afoul of US authorities, of being deported and/or imprisoned, and --importantly--of being permanently banned from the US. This is a tremendous disincentive for trafficking victims to come forward. In effect, the traffickers are using US immigration law against their victims.
One might argue that putting such a broad amnesty in place creates a back door to immigration, that the system will be ripe for abuse. Perhaps. But personally, I am a great deal less concerned about someone getting into the US on a false pretense of being a victim of trafficking than I am about the trafficking happening under our noses going unpunished.