Here's the opinion in U.S. v. Gould
...which is the case I referred to below. Seems the police had a tip that Gould was going to kill two judges. They went to his trailer and were admitted by a roommate named Cabral. They do a "protective sweep" of the trailer for Gould, including his bedroom. No Gould. But they search under the bed and in the closets, and in one closet they find...three rifles. Eventually they find Gould outside in the woods. He says the guns belong to somebody else, but that's beside the point.
Which is...Cabral had no authority to consent to a search of Cabral's room, so did the police have the right to search it anyway under the "protective sweep" exception to the warrant requirement? Note that it wasn't incident to arrest, because they seached the room before they found him. Normally the "protective sweep" exception applies to search incident to arrest. So that's why this case is so unusual.

I think this case will draw some commentary from legal beagle types. Will the USSC get involved? Who knows...