Wait what? Maybe his engine was running to run the freezer to keep your ice cream cold?
If he was ignoring regulations on energy efficiency, it's very possible he was also ignoring regulations on health and hygiene.
I asked the trader to use the socket, rather than his engine, since the diesel fumes were coming into our office, and the adjacent building was a primary school. He refused, so I reported him to the local council. They referred it to the police, since the van's number plate wasn't in their records.