A big problem with NAFTA and the TPP
...is that the pro-corporate sections are enforceable; the environmental sections are unenforceable.
Corporations can get their way under these treaties with arbitration panels called "Investor-State Dispute Settlement (ISDS)." Environmentalists don't have access to those panels.
Critics of ISDS include Senator Bernie Sanders (I-VT), Senator Elizabeth Warren (D-MA), and the co-chairs of the Congressional Progressive Caucus, Reps. Raúl M. Grijalva (D-AZ) and Keith Ellison (D-MN).
http://cpc.grijalva.house.gov/press-releases/progressive-caucus-cochairs-on-transpacific-partnership-agreement/
President Bill Clinton passed NAFTA. Secretary of State Hillary Clinton helped write the TPP.
Hillary Clinton says that she recently decided against the TPP because of concerns about the issues of labor and pharmaceuticals and currency manipulation.
She apparently isn't concerned about ISDS. If she becomes president, we'll probably get more treaties with ISDS.