Aren’t Licence Plates and Drivers Licences provided by the Dept of Motor Vehicles? Which is under the governance of the State Police?
The plates are technically the property of the state and register your car, you, all your personal information, your criminal record with the Police database. It’s pretty much the only thing it’s designed for.
Cops routinely do licence plate checks, it’s their job. It’s how they can find parole breakers, people who don’t pay child support, stolen cars, kidnapped children. They do not need any warrant whatsoever, all that information you provided to them, and it’s critical to any investigation.
Interestingly enough, they do protect it as well… You can’t just call up or go to a web site to look up a licence plate. You have to file a request with a reason, or a complaint. A private detective can do this but it costs $$. Basically you have to file for a warrant to get it.
As for tracking plates, that’s just data gathering, and bear in mind, the police can put someone under surveillance for any reason, no warrant. But, since they really don’t have enough people or time, doing something like that would only be for really good reasons.
I totally agree about the dragnet crap that the NSA is doing… mainly 'cause it’s a huge waste of money for absolutely no results. But don’t bulk in legitimate investigation methods because we actually need those to work.
Lastly, all this stupid data collection won’t actually prevent any crimes, it may possibly help an investigation, but even more likely it could help innocent people by knowing their whereabouts and that they couldn’t be at the scene of the crime.