Law seemed to have a reaction of surprise when Caesar offhandedly mentioned the kids would want to come back on their own. That made me think Law doesn't know they have been made drug addicts to have absolute control over them.

Just to be clear, I wasn't suggesting Law is as stupid as the chimera pirates and believe Caeser is some great humanitarian. I'm just predicting he doesn't know everything, like about making the children junkies. Law is probably there to learn or acquire something related to his interest in medicine, so it would make sense Caesar doesn't share anything unnecessary with him. If Law is to have some sort of continuing understanding with Luffy, torturing children is probably beyond the line he can cross. But then again, if he's not to have such a relationship, then everything goes. I'm merely basing that on the past events where he suddenly showed up to help Luffy.