Yes that may be the law, but what I have found full timing with my pets is it is the PUBLIC not law enforcement that starts screaming and causing problems with pets in RV's.
I had a breakdown with a tire in Texas and the temperature was 112 degrees out and I had pulled into a gas station and was waiting for a ERS tow truck to arrive.
I left the MH to go inside the gas station to get a cup of coffee. The dogs started barking in the MH and when I turned around a crowd of people where heading for my MH literally screaming,
"OMG there are dogs in the RV let's go get them out before they die". :S
Ya like they were going to die inside the MH with the gen running and the AC on.