I found a couple of 5-minute idling ordinances in my searches, and an ordinance against leaving vehicles unattended and idling on highways.
However, I found nothing in your link that says it's illegal to leave a vehicle running and unattended in a parking lot, as the cop contends.
Can you provide a quote from the link that backs the cop's contention?
Apparently idling in the headline was wrong.
From the article: “...leaving the ignition key in an unattended vehicle”