The Fourth Amendment states that "no Warrants shall issue, but upon probable cause." Anticipatory warrants are warrants that issue without probable cause; the probable cause comes after the warrant has been issued.I posted a comment on that thread, basically making the following point:
Note how Breyer replaces the textual requirement that "no Warrants shall issue, but upon probable cause" with a somewhat different inquiry into whether the warrant "can help assure that the search takes place" when probable cause exists.
A judge's role, in issuing a warrant, is to decide whether the facts, as represented by the police, constitute probable cause. It is not the judge's role to test that representation. If the police turn out not to have told the truth, then the warrant can be challenged, and retroactively invalidated.
Here, the judge is giving the police exactly the same trust: to say that the event that would constitute probable cause has happened. What difference does it make whether the police make that determination before or after the warrant is issued?
I don't see anything in the text of the amendment that says the probable cause has to exist at the time the warrant issues. All it says is that the warrant shall not issue except on probable cause; it doesn't say whether this probable cause has to exist at the time the warrant issues, or at some later time.
And this way, the police can't claim that they didn't know what was relevant. They've been told in advance what to look for, and if it doesn't happen they're on notice that they can't do the search.