With each attempt to clarify the "minimum standard of treatment" in investment obligations, the scope becomes less clear to me. Here's what the leaked CETA text says (page 158):
Article X.9: Treatment of Investors and of Covered Investments
1. Each Party shall accord in its territory to covered investments of the other Party and to investors with respect to their covered investments fair and equitable treatment and full protection and security in accordance with paragraphs 2 to 6.
2. A Party breaches the obligation of fair and equitable treatment referenced in paragraph 1 where a measure or series of measures constitutes:
(a) Denial of justice in criminal, civil or administrative proceedings;
(b) Fundamental breach of due process, including a fundamental breach of transparency,
in judicial and administrative proceedings.(c) Manifest arbitrariness;
(d) Targeted discrimination on manifestly wrongful grounds, such as gender, race or religious belief;
(e) Abusive treatment of investors, such as coercion, duress and harassment; or
(f) A breach of any further elements of the fair and equitable treatment obligation adopted by the Parties in accordance with paragraph 3 of this Article.
3. The Parties shall regularly, or upon request of a Party, review the content of the obligation to provide fair and equitable treatment. The Committee on Services and Investment may develop recommendations in this regard and submit them to the Trade Committee for decision.
4. When applying the above fair and equitable treatment obligation, a tribunal may take into account whether a Party made a specific representation to an investor to induce a covered investment, that created a legitimate expectation, and upon which the investor relied in deciding to make or maintain the covered investment, but that the Party subsequently frustrated.
5. For greater certainty, ‘full protection and security’ refers to the Party’s obligations relating to physical security of investors and covered investments.
6. For greater certainty, a breach of another provision of this Agreement, or of a separate international Agreement, does not establish that there has been a breach of this Article.
It's interesting to note that there is a general exception in CETA that incorporates GATT Article XX (page 463):
Article X.02: General Exceptions
1. For the purposes of Chapters X through Y and Chapter Z (National Treatment and Market Access for Goods, Rules of Origin, Origin Procedures, Customs and Trade Facilitation, Wines and Spirits, Sanitary and Phytosanitary Measures, Investment Section 2 (Establishment of Investments) and Investment Section 3 (Non-discriminatory Treatment)), GATT 1994 Article XX is incorporated into and made part of this Agreement. The Parties understand that the measures referred to in GATT 1994 Article XX (b) include environmental measures necessary to protect human, animal or plant life or health. The Parties further understand that GATT 1994 Article XX (g) applies to measures for the conservation of living and non-living exhaustible natural resources.
However, only Section 3 of the investment section is covered, and Article X.9 (quoted above) is in Section 4. In other trade agreements, by contrast, Canada has created an exception that applies to all investment obligations (see, e.g., Article 23.02, para. 3 of the Canada - Panama FTA).
There's also an explanatory note to Article X.02 which says:
Negotiators’ Note for legal scrubbing: The application of GATT Article XX to various CETA
chapters will need to be reviewed in light of the actual content of these chapters. ...
So it sounds like this may be an area where negotiating is still going on.