Historically, though, the Black Hills were only Lakota land for a little under a century, and they obtained it via warfare with other tribes...then lost it via warfare with the U.S. government, so there's a certain symmetry there. The violation of the treaties by the U.S. gov't isn't much in question, though.

It's unclear whether this was just a group of activists trying to make a point, or an act of the actual elected Sioux representatives. My bet is this is just a symbolic act with little real consequence one way or another.