The TPP "Drafter’s Note on Interpretation of 'In Like Circumstances'" is here.
In paragraph 2, it says: "Articles II.4 [NT] and II.5 [MFN] do not prohibit all measures that result in differential treatment. Rather, they seek to ensure that foreign investors or their investments are not treated less favourably on the basis of their nationality."
To me, these sentences are kind of a big deal, if they establish that NT and MFN are only about nationality-based discrimination, rather than "best treatment" or some other concept.
Of course, then you get into questions of what "nationality-based discrimination" means, and where you look at that issue. Note that the drafter's statement was made in the context of interpreting "in like circumstances," when perhaps it belongs under an interpretation of "treatment no less favorable." Along these lines, in paragraph 3, the note says:
Accordingly, the Parties agreed to include a new footnote in the text: “For greater certainty, whether treatment is accorded in ‘like circumstances’ depends on the totality of the circumstances, including whether the relevant treatment distinguishes between investors or investments on the basis of legitimate public welfare objectives.”
This sentence talks about distinguishing "between investors or investments," and doesn't mention nationality. That could, I think, lead to the kind of analysis where you look at only two investors/investments, without considering the entire group of investors/investments, comparing the treatment of foreign ones to the treatment of domestic ones. If we want to be certain that NT and MFN are about nationality-based discrimination, the clarification on this issue may need to be made in the context of "treatment no less favorable."
