As I read it, that is covered by Art IV, Sect 2. Unfortunately, it doesn't say WHO is supposed to deliver the perp back to the original state. I would think that unless a federal police force is authorized elsewhere it's implied that it would be the state that is fled to which is responsible.
Darth - we have Federal Marshalls, I’m 100% in favor of using their authority to arrest pedophiles.
There are a million in one areas where the Federal Government should get its nose out of, but I’m not sure shielding pervs is the place I would start.