It should be illegal.
The system should immediately purge any and all license plates that are not part of a current investigation. Otherwise they are placing millions of people under illegal surveillance.
If they want to make it legal to spy on everyone all the time just in case it proves useful 5 years latter then they need to do so by passing legislation that clearly and explicitly authorizes them to do that.
If that fails on constitutional grounds push for a constitutional amendment.
Although good luck trying to do that without committing political suicide.
I'm surprised frankly I'm surprised that there isn't widespread use of State Ballot Measure as a backlash against this kind of thing.