It seems a serious problem has arisen with the new laws legalizing marijuana in some states. Drug sniffing dogs have been trained to act upon detection of any controlled substance they sense. All a drug smuggler or even a user of heroin, cocaine, etc has to do is have some marijuana in the vehicle and if the dog signs illegal drugs and the more serious drug is found it will be argued in court it was an illegal search because the dog hit on the marijuana, triggering the search. This is a serious problem because it is almost impossible to re-train a dog to ignore marijuana.
It would appear the only solution would be to train all new dogs. There is always, it seems, something not considered when new laws are passed. And so it goes.
Ken