Anticipatory Warrants, again

Pretty much the same as last time. Orin Kerr once again called for comments, this time stating in his own voice:

Am I missing something, or does the text of the Fourth Amendment answer this question for us? The text says that no warrants shall issue, but upon probable cause. In this context, it seems to me that "upon" means "following the establishment of" and "issue" means "signed by the judge." If that’s right, doesn’t the plain text of the Fourth Amendment prohibit anticipatory warrants?

. I replied in comments, much as I did then.

What makes you think that "upon", in this context, means "after", rather than "on the grounds of"?

Orin wrote:

If the constitution said, "no
warrants shall issue, but based on probable cause," or "no warrants
shall issue, but on the grounds of probable cause," doesn't that still
prohibit anticipatory warrants?

My answer: No, it doesn't. That's why you originally wrote: 'In this context, it seems to me that "upon" means "following the establishment of'; and if that's what "upon" means, then you're right.

But I don't think that is what it means. All it means, I think, is that the grounds for the warrant must add up to probable cause. So when the police tell the magistrate the facts as they know them, if he thinks they don't add up to probable cause, he must not issue the warrant, and if he does issue it then it's invalid. Similarly, if what the police told him turned out not to be facts after all, then his decision that they added up to probable cause is irrelevant, and the warrant is retroactively invalid.

But nowhere does it say that the magistrate's assesment of the facts, and decision that they constitute probable cause, and the consequent issue of the warrant, must occur after the facts themselves. All the magistrate is doing is issuing a legal opinion, based on a set of givens. If X and Y and Z are all true, then probable cause exists, otherwise it doesn't. He can do so when X and Y and Z are all true, or he can do so before they become true; if they never do, then his opinion, while still true, is irrelevant.