@SecondJon
I believe a government definitely has a responsibility to protect the rights of it's citizens. As slavery is the encroachment upon the rights of the enslaved, the government does have a role to play in stopping slavery of any kind, including sex trafficking/child slavery.
As far as how to do it, I'm not so sure on that one. I think a big issue is people being able to recognize signs of trafficking/slavery, and being able to report it. A lot of the push has to come from the citizens.
I look more to the model of OURrescue.org to fight this evil. It is a volunteer driven organization that works with governments to stop slavery. I think this organization with it's raining and experience would provide good insight into how to fight this.