No, I don’t know the case. I’m going to have to look up US v Williams.
Scalia sees the Grand Jury separately from Articles I, II, III since it’s in an amendment. At the same time, Art III says the judiciary has jurisdiction over all cases....something like that.
Here’s a link to the case that contains Scalia’s comments.
http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=us&vol=504&invol=36