To what extent does a tobacco carve-out protect public health in the Trans-Pacific Partnership Agreement?

In November 2015, negotiations of the Trans-Pacific Partnership Agreement came to a close with the release of the final text. It included an optional carve-out (exclusion) for tobacco control measures from the TPP's investor-state dispute settlement mechanism. Despite the apparent 'win' for the field of tobacco control, the limited scope of the carve-out provides only partial protection for public health regulatory measures.