"How can law enforcement possibly police this?"
Given that breaching copyright would be classified as a criminal offence with the TPP, and meta-data access is only for criminal purposes, meta-data and an automated system can be used. So once the system is in place, very easily.
"C'mon, seriously? Is there anyone who doesn't know risk of imprisonment doesn't act as deterrent. There are Australian's about to be executed in Indonesia for drug trafficking. Should be pretty obvious."
Risk of imprisonment may not deter some, but it may deter enough for them to feel its worth it.