This just seems weird to me (article):
Major is an extremely sociable dog that “loves to search for narcotics,” Watson said.
Barking during a drug search isn’t a threat, Watson said. Dogs are taught to treat finding drugs as a game of hide and seek.
“Why is a dog barking?” Watson said. “It’s not because it wants to bite someone. He just wants to play that game.”
Some dogs are trained as passive alert dogs and will sit when drugs are found. Others are aggressive alert canines and bark or take other actions.
It’s a game kids, it’s all a game. We teach Scraps that biting your face off is just a game, so when he’s biting your face off that’s alright because he’s just playing the game.