In the U.S. first written submission in the Article 21.5 WTO panel proceeding in U.S. - Tuna II, the U.S. distinguishes Tuna from Seals in regard to non-discrimination. Here's the GATT MFN section:
287. The facts here are in contrast to the ones in EC – Seal Products where the Appellate Body recently found a breach of Article I:1. There, the market access advantage was subject to eligibility conditions related to immutable characteristics (such as the racial/cultural identity of the seal hunters) such that while virtually all of the products of Greenland were likely to qualify for access under the measure at issue, the vast majority of the products of Canada and Norway were not.
288. But here, the conditions of eligibility relate to fishing methods. And there is no one way to fish for tuna. Fishermen have a choice about how they fish. By no means is setting on dolphins required inside (or outside) the ETP to catch tuna. Indeed, even in the ETP, only 40 percent of the sets by large purse seine vessels are sets on dolphins. The eligibility conditions – and therefore the opportunity for the label – are the same for everyone.
And here's the GATT National Treatment section:
310. The Appellate Body’s analysis in EC – Seal Products does not suggest a different conclusion. In that dispute, Canada and Norway challenged an EU import ban on seal products that provided for two notable exceptions: seal products produced by qualifying indigenous communities (IC) and products from managed resource management (MRM) hunts were allowed to be sold in the EU. The panel found, and the Appellate Body did not disagree, that these two exceptions were drawn in a way that benefited only EU member States, while the seal products of the two complainants were almost completely excluded from the EU market. Furthermore, in light of the fact that eligibility for the IC exemption depended on immutable characteristics (such as the racial/cultural identity of the seal hunters), the vast majority of complainants’ products could never qualify for this exception.
311. In sum, there were sufficient facts on the record for the panel and Appellate Body to determine that the challenged measure was de facto inconsistent with Article III:4.
312. But those type of facts are not present here. The amended measure has no exceptions – the eligibility requirements apply to all tuna products. And those eligibility requirements relate to fishing methods, which is not an immutable condition. Any Member may produce non-eligible tuna products one year and eligible products the next year, depending on the different choices that its fleet makes year to year. Indeed, at the time of the enactment of the DPCIA, a substantial amount of tuna product produced by the U.S. fleet was not, in fact, eligible for the label, and that portion of production only became eligible after a few years had passed. Finally, there is simply no evidence on the record that the amended measure singles out Mexico and its producers. Setting on dolphins really is dangerous for dolphins. That was (and is) the focus of the concern. Who produces the tuna product is entirely irrelevant to the United States.
Is Tuna different enough from Seals that there will no violation found here?