Consider this:
The Treaty calls for the US government to protect the tribal reservations from physical threat and judicially. IE when the tribes sued in Boldt, they were represented by the the federal govt and the case was called "USA vs State of Washington."

If the Corps had OK'ed the ramp, and the tribe decided to file suit against the Corps, it would be "USA vs Army Corps of Engineers (USA)".
How does that work? Think legal council at the Corps might have been influenced by that, possibly interfering with the factual merits of the permit?

Second: It strikes me as odd that the Corps decision had to do with defining treaty rights, and if this ramp infringes on their ability to harvest within treaty specifications. (It is a gray area that takes some debate.)
Why is it in the Corps jurisdiction to define legalese on a treaty? I thought only Congress could do that?
I would have thought the Corps looked at structural, environmental/ESA, and hard permitting/construction requirements, not legal interpretation of hypothetical claims...especially when there is no appeal process.