This is from the EU's first written submission in the European Union — Measures Related to Price Comparison Methodologies (DS516) case (footnotes omitted):
8. STANDARD OF REVIEW: PERMISSIBLE INTERPRETATION
275. The European Union submits that the special standard of review in Article 17(6)(ii) of the Anti-Dumping Agreement applies in this case. That special standard of review refers to "the Agreement", meaning the Anti-Dumping Agreement. However, in this particular case the Panel is called upon to interpret the relevant provisions of Article VI of the GATT 1994, the Anti-Dumping Agreement and Section 15 of China's Accession Protocol in such a way that they "apply" and are "consistent". A pre-requisite for interpreting two applicable documents in a manner that renders them "consistent" with each other is that one is using the same tools and standards of interpretation: otherwise the requirement that the two interpretations be "consistent" would be meaningless.
276. The European Union is familiar with the case law concerning Article 17.6(ii) of the Anti-Dumping Agreement according to which one first applies the customary rules of interpretation of public international law, which in turn implies that normally there may be but one correct interpretation that ultimately prevails.
277. However, without entering into that particular debate, the European Union would like to point out that the DSU is without prejudice to the rights of Members to seek authoritative interpretation of provisions of a covered agreement through decision making under the WTO Agreement. In this particular case, through "decision making under the WTO Agreement", and specifically through a decision to conclude the Accession Protocol with China pursuant to Article XII:2 of the WTO Agreement, all of the Members have agreed to the interpretations of the relevant provisions of Article VI of the GATT 1994 and the Anti-Dumping Agreement reflected in China's Accession Protocol, both before and after 11 December 2016 (in addition to the China-specific rules contained therein). Those interpretations must certainly be considered to be authoritative, emanating as they do from the entire Membership, acting by consensus. They must therefore also be considered to be permissible within the meaning of Article 17(6)(ii) of the Anti-Dumping Agreement.
278. This observation is further confirmed by Article 31(3)(a) of the Vienna Convention, which provides that there shall be taken into account, together with the context, any subsequent agreement between the parties regarding the interpretation of the treaty or the application of its provisions.
279. The European Union concludes that it is permissible to interpret the relevant provisions of the Anti-Dumping Agreement as meaning that, in the event of a lack of comparability, including, for example, a market situation that is not normal, but rather particular, an investigating authority may reject affected prices and costs and use instead information from a third country, adjusted where necessary. As the final sentence of Article 17(6)(ii) of the Anti-Dumping Agreement provides, a panel must uphold a measure if it rests upon such a permissible interpretation.
The EU thinks it has come up with a narrow set of circumstances in which 17.6(ii) will have an impact: Where there is an authoritative interpretation by the Members. Will the panel accept, as a general matter, that authoritative interpretations can lead to an additional, "permissible" interpretation? And will it find that, in this case, there was an authoritative interpretation of this sort?
I haven't seen any discussions of this issue in the U.S. submissions that are available so far, but we are sure to hear from the U.S. on this.
ADDED: I don't know why you need Article 17.6(ii) for this argument. If you have an authoritative interpretation of some sort to support your position, why does 17.6(ii) matter? If authoritative interpretations apply outside the context of the AD Agreement (and presumably they do), where there is no 17.6(ii) equivalent, I'm not sure you need to rely on 17.6(ii) for this in an AD Agreement case.