SCOTUSblog has a preview of the oral argument tomorrow in United States v. Grubbs, the anticipatory warrant case. (For my earlier posts on this case, see here and here.)

  The argument promises to be fascinating. The defendant's brief makes a direct textual and historical challenge to the very concept of anticipatory warrants, and it's the kind of argument that I think should be very appealing to Justices Scalia and Thomas. The argument is that the Fourth Amendment's warrant clause means what it says: "no Warrants shall issue, but upon probable cause." Anticipatory warrants are warrants issued before probable cause exists; the idea is that when a future event occurs, probable cause will exist, so the police can execute the warrant whenever it happens.

  There are reasonable policy arguments for why anticipatory warrants don't disrupt this scheme very much, at least if regulated carefully; Justice Breyer endorsed them back when he was on the First Circuit. But my guess is that Scalia and Thomas are going to focus heavily on the text of the Fourth Amendment instead of the policy arguments, and a few other Justices are going to be worried about how anticipatory warrants can water down the warrant requirement. Stay tuned.