When you read the text of Marshall II, I think they're spelling out what happened with the potential justification arguments that were put forth in Marshall I. In essence, what happened in Marshall I was that the Crown was arguing that there was no treaty right to the activities that Donald Marshall Jr. was involved with, and therefore, they didn't feel that they needed to put forward justification arguments on whether or not he did have a treaty right, but there were conservation concerns, or whatever, at the time. At the time, the Crown chose not to provide justification arguments, and when you read Marshall II, you see that's one of the points that is brought up, that some people felt that it should have taken place.
