Addressing:
While "Indian tribe" is official US Gov't lingo, saying "tribe" twice in the first sentence and then again in the second is awkward, also "the tribe" is not a monolithic entity, but rather a collection of people - so maybe reword to say something like "The Coeur d'Alene people once inhabited 3,500,000 acres (1,400,000 ha) in northern Idaho and Washington,[2][3] (And Montana, actually, note article on the tribe) but today, the only land controlled by the tribal nation is the Coeur d'Alene Reservation in Benewah and Kootenai counties, Idaho.[4]" You don't have to use my wording, but you see how I am distinguishing land and people, though the two are, of course, closely intertwined.  
.  Boomer!  
Second and third paragraphs jump around and need another copyedit. I'd put right up front that Johnson did the executive order but Congress never acted on it, then go on about how the tribe didn't accept it anyway?  Keep the chronology clearer.   (Interesting that the Coeur d'Alene article says nothing about this period, maybe finish here and add a bit to that article too... hmmm) 
From a VERY cursory review of the decision, it appears that gap between creation of the reservation and Idaho's statehood becomes significant in this case, so perhaps give us a bit of foreshadowing that this is not just a dry fact, but it's something that's going to matter.  
The section fails to draw out the significance of the info on the state park and mining, maybe add a wee bit to hint at why this will matter in the SCOTUS case.