I haven't left, thanks for all responses. To this date i still haven't found an actual regulation that prohibits dual controls when pax is sitting in copilot seat. I have however found in the aircraft manual that eurocopter recommends the removal but does not say it is mandatory.
I will like to add, this dodgy business isn't being practiced, the idea is out there, hence why i am looking for regulations to stop it in case the company/captains allow it.