If it were me who they stopped I would be down at the police station to inform the duty officer about what happened, in the nicest possible way. In your case, be very nice, especially with a van that is easy to spot and "pick" on in the future. Tell them that through the officers lack of knowledge you are losing earnings. 
  
As said on another post, print out the Wildlife act and keep it in your vehicle. You should as a pest controller know the law to. 
  
On the chip scanner, he might have been a wildlife leason officer, which makes it worse if he doesn't know the law.