A couple of things in the TPP improve upon NAFTA. The NAFTA ISDS provisions have been interpreted by arbitration panels in a way that has largely favoured Canadian laws and regulations. We've won many important disputes under the NAFTA.
The TPP defines more precisely the basic concept of equitable treatment. Under the TPP, as under NAFTA, countries are required to provide fair and equitable treatment for all investors. The TPP narrows that very important concept and says that has to be a precise concept agreed to under international law, and not just a vague, open-ended concept that the arbitrators can apply.
It also provides that regulatory changes in themselves are not offensive of the treaty. In other words, you can't claim, as an investor, simply because there's been a change in regulations that might impact on your investment in some way or another. There are also a number of other off-ramps for public policy issues affecting the environment, public safety, public health, and other things.
There's an important narrowing of the scope of ISDS in the TPP.