We have no reason to think courts would find (A) less compelling in the future. The author indicates that natives’ lack of evidence of ownership will be a less compelling piece of evidence. But evidence that the natives did not have original ownership is different. “Natives can’t prove they own X” is different from “There’s evidence the natives didn’t own X.”

This confuses natives with the museum. The fact natives can’t produce written evidence of ownership will be a less compelling reason to rule in favor of the museum. But the museum’s lack of evidence is a different issue.

The fact natives can’t produce written evidence will be a less compelling reason to rule in favor of the museum. But if natives can produce such evidence, we have no reason to think the court would find this less compelling.

The author suggests courts will treat (D) as a less compelling reason to favor the museum. Currently the fact that natives rarely possess evidence of ownership makes courts more likely to rule in favor of the museum. But courts will start to honor natives’ claims to cultural property even if they can’t demonstrate ownership under the notion of private property.

The fact groups of native Canadians don’t have the concept of private property isn’t one of the reasons courts currently find in favor of museums. Rather, it’s the natives’ lack of evidence of ownership that leads courts to find in favor of museums. So what (E) describes can’t become a less compelling reason for deciding in the museum’s favor, because it isn’t even a reason in the first place.