It’s not that police can’t use tools that arent available to the general public. It’s that in the US we have the plain view doctrine which defines the boundary between the things that can be plainly observed in public, which don’t constitute a search and thus don’t trigger the 4a protections, and observations that are not plain view observations and which are a search and trigger 4a protections
OP's contention is that private citizens don't have access to a network of cameras to look for license plates and therefore it isn't "plain view", but I don't see how that's different than law enforcement being able to muster the entire nation's cops to look for a suspect.
Because it is not about some principle that cares about the nature of the action, the principles are related to the civil liberties at risk, and whether or not certain powers jeopardize them.
The level of observability and risk involved in using the entire nation’s police resources is extremely high, whoever asks for that much resources will have to account for what they are doing and many of the details of the event are likely to be scrutinized by many parties, media, other departments, etc. It is unlikely to be wielded to abuse or strip civil liberties or to harass people, as we’ve seen ALPR’s be used
- counting the number of vehicles going by
- radar’ing every car to produce a report on how many people are speeding and how much
- checking all licence plates for valid registrations to produce a report on what percentage of cars have expired tags on the road.
