"I think that something as serious as correctly performing a drug/alcohol test and/or preventing a person from proceeding to their aircraft (whether guilty of something or not), should only be done by fully trained officers of the law."
a very quick way to criminalise the whole procedure..... everyone could.should be tested but a nurse would be far more cost effective and probably better at talking people into a remedial proggramme. The police will be very tempted to arrest & charge anyone