A few observations.

It’s an oversimplification to say the Treaties trump the MMPA (or the ESA). The Federal agencies responsible for implementing the MMPA/ESA also need to uphold the Treaties. So they need to do both. It may be difficult, but it can be done.

There may be a situation where the MMPA/ESA and the Treaties are in conflict, and become completely intractable. In that case, it’s possible a judge would be asked to decide which takes precedence. But all sides of this debate would go to great lengths to avoid that question. Nobody wants to risk getting an answer they don’t like. So it would likely get settled before getting to court. The last issue that went to the SCOTUS (the Culvert Case) regarding Treaty rights gave the Tribes a real scare so it’s likely they will be very cautious before going down that road again.

(Recall the Culvert decision was 4-4 split, with Justice Kennedy recusing himself. So the case was never really decided, except that the 9th Circuit Court decision stands, but is only applicable in Puget Sound. If the SCOTUS had made a decision (e.g., 5-4), the result would have applied nationwide. For better or for worse.)

Also, yes the Makah Tribe’s treaty includes the right to take whales. But ‘whaling’ and ‘sealing’ might be considered different activities. Whaling is an obvious treaty right while sealing may or may not be considered consistent with whaling (as the Tribes would have understood it). So taking seals is not as clear as the right to take whales.

My sense is that if the Makah Tribe wanted to kill a bunch of seals under their Treaty, they probably can. They might not get dragged into a legal fight, but the public relations pushback would be severe, just like it was when they killed a grey whale 20 years ago. They’re probably not anxious for that to happen again, particularly since seals are probably not high on their list of favorite foods.