Well, the Courts are implicit in every suit. Where, in the article, does it say that this motion was filed by anyone other than the Indian tribes?
"Attorneys for the Colville, Nez Perce, Umatilla and Yakama tribes recently filed a motion with the court saying that the study would "irreparably harm the tribes' ownership and property interest in the remains" and would result in destruction of the bones "in both the physical and spiritual senses." They filed the motion after U.S. Magistrate John Jelderks in Portland rejected their request to delay the study. Jelderks ruled last August that the scientists could study the remains. "
Other parties being involved in the case doesn't mean that the Tribes didn't file this motion by themselves or for their own reasons. In fact, it should be assumed the motion was filed for their own reasons. The article states this specifically. And, if the article is correct, It was the anthropologists that filed the original suit against the Corps of Engineers, for unspecified reasons. The Indian tribes may have involved themselves into the case as interested parties. In the current ruling (as reported in this article), it appears that the Indians alone are trying to prevent the study, or delay it till they can get their attempt at preventing it before a higher court.