Don't they?. If you tell the cops that your neighbor has drugs of significant quantity in their house, would they not still need a warrant to actually go into your neighbor's house?
There are a lot of nuances to these situations of third-party involvement and the ruling discusses these at length. If you’re interested in the precise limits of the 4th amendment you should really just read the linked document.
they should as a matter of course. but I guess "papers" you entrust to someone else are a gray area. I personally think that it goes against the separation of police state and democracy, but I'm a nobody, so it doesn't matter I suppose.
