So what are alternative ways to catch criminals? Wait for them to show up at the police station? There's a big difference between mass surveillance and surveillance. I want cops to be able to do their job. I don't want my information collected to be used against me in a crime I haven't yet committed. This is the NSA debate: warrants should be required for a suspect that is under suspicion; but not everyone should be mass surveilled "just in case."

I would feel better about this if the license plate readers simply pinged law enforcement on a real-time match. The storage and potential data mining aspects are where it crosses the line. Stasi stuff there.

Or, make a warrant required, and only enable collection of data where a proper warrant for a specific plate is in place start collection, in a granularity of N-days (being as few as one and as many as say 30, without another warrant).

The system should be unable (by design) to store information on plates without warrant.. as you mention, in terms of a ping... No historical logging of data outside that scope.

Cops are able to start following someone... they aren't able to go back in time and start following someone three weeks ago.

That design is way too easy to switch into full recording mode. It feels like as much of a solution that DRM is.

True... and barring fictional "investigations" could be challenged in court. The problem is, we're rapidly reaching a point close to 1984 in terms of privacy (or lack of).

If I were going to craft such an amendment, I'd probably make a distinction between active monitoring and passive monitoring and require reasonable suspicion to switch to active.

If I go shoot up a theatre, the police would allowed to put an active trace on me and query their database.

They wouldn't be allowed to just search for drug users by investigating who goes near drug corners.