[QUOTE=DSYoungEsq]
EXACTLY WHICH OF YOUR RIGHTS HAVE THEY VIOLATED??
Sorry to shout, but this is the crux of the whole stupid issue. “Probable cause” is needed for only two things: searching something or someone which is private, and seizing a person or property.
Running a computer check to see what information exists in the system does neither. It does not search you or your property. It does not seize you, or your property.
Therefore, there would be no constitutional issue with an officer running a check on random tags, or even on every tag he sees.
There MAY be legal issues unrelated to the Fourth Amendment. A state can always voluntarily limit access to a database through passage of a law. And a police department, or a particular jurisdiction with some department that has police powers, could always voluntarily restrict such searches if they chose (perhaps to avoid the uneasiness of the public at having the police running checks for no other reason than to see if they have a grounds to hassle someone).
But a constitutional issue it is not. If you think it is, I refer back to the top of this answer: What Right do you think they have violated? Be specific: Scalia will insist upon it. 
[/QUOTE]
Sorry, I didn’t mean just running the tags violated probable cause, I meant, what if they act on information they would not have had, and would not have acted upon, without running the tag? For example, you have visible tags that are not expired. They run the plate anyway and find the tag does not belong on your car,or that the car owner has outstanding warrants. You had valid tags, they had no reason to run the check, but now pull you over, maybe arrest you, for something they would not have been able to surmise without unnecessarily running the tag.
If my definition of “probable cause” still does not jive with this scenario , my apologies. But the definition I have includes not only search and seizure, but arrests as well.