You don't even need to define it - you can half-ass it and rely on courts to clarify the edge cases. That's how the vast majority of laws work.
replyThis is also true, but we’ve seen the problems with that idea put on display pretty prominently, lately.
replyYeah, but we don't want cameras everywhere, not just auto plate readers.
replyWhat is the difference between a security camera watching the municipal tools shack entrance and the security camera watching the main road?
The ultimate goal is to not have a massive database of everything that happened everywhere going back forever. So it even extends far beyond just reading license plates.