One point that everyone seems to be missing is this:
This law is a restriction on honest citizens who are minding their own business. It was created because of CRIMINALS, supposedly to protect citizens from criminals. The real solution would be better policing and rounding up the criminals who steal cars.
In most places, police make no effort whatsoever to recover a stolen car or to catch the thieves. So this law became necessary because of police REFUSING TO ENFORCE already existing laws. By refusing to enforce, they sent the message to car thieves that stealing cars is a low risk enterprise. In effect they have invited the thieves to steal.
When the cops start doing their jobs, the need for stupid laws like this one will go away.
For most people, their common sense would tell them leaving a car running without the driver can get people hurt or killed. Thus you get this law.
#1: If car engages due to mechanical failure possible dead people.
#2: Some minor goes by, sees the operating car and takes their first self-driving lesson. Possible major problems right there.
Yes, a slightly small chance, but significant enough to not risk it.
The same justification this cop gave will be the same one that will be used in the future to justify putting trackers on everyone’s cars.