Even if there have been few observations on the Biotech ruling from the perspective of the WTO-MEAs (Multilateral Environmental Agreements) debate, the fact is that the MEAs aspect of this ruling has apparently added something to this debate, although the ruling is puzzling through its ambivalence.
1) On the one hand, this ruling does not hesitate to agree with the EU that " a treaty like the Biosafety Protocol would qualify as a rule of international law" in the sense of Article 31(3)(c) of the Vienna Convention. Therefore, instead of the usual tendency of panels to disregard public international law or to confine it simply to interpreting certain terms such as "natural resources", we have here a solid affirmation that public international law matters for interpreting WTO agreements.
Of course, the Biotech panel took great care to add that Article 31(3)(c) mandates a treaty interpreter only " to take into account" of the Biosafety Protocol and "thus no particular outcome is prescribed." The fact remains however, that the panel did not hesitate to affirm that if there is more than one permissible interpretation of a WTO agreement, then " Article 31(3)(c) in good faith would in our view [lead] to settle for that interpretation which is more in accord with other applicable rules of international law"
What would have been the consequence of this attitude if the Panel had found that the Biosafety Protocol and the Convention on Biological Diversity effectively apply because all parties to the Biotech dispute were bound by these treaties? We'll never know if the panel would then have been ready to call into question the " exclusive character of the DSU for WTO-related disputes". I suspect that the panel was very happy to see that not all the parties to the Biotech dispute were members of the MEAs , avoiding thus to rule on this point.
2) On the other hand, after indicating clearly that other rules of international law which are "applicable in the relations between the parties" could matter in WTO disputes, the Biotech panel gave a heavy hint that the word "parties" could mean here all WTO members. In the words of the panel " Article 31(3)(c) does not refer to "one or more parties" [nor] to "the parties to a dispute ". Even if these affirmations were in fact obiter dicta, they would mean, if confirmed, that for all intents and purposes most MEAs are useless in WTO disputes. Here again the Biotech panel was certainly very happy to see that the Biotech case was not one in which "relevant rules of international law are applicable in the relations between all parties to the dispute, but not among all WTO Members." Therefore, the panel didn't have to take position on whether in such a situation it would be entitled to take the MEAs into account.
From the perspective of the MEAs debate, it is perhaps unfortunate that the Biotech ruling has not been appealed.