$1:
How long has he been in?
If its more than 5 years, flags may start to go up if he hasnt taken a tour. The system will most likely be very easy on him at first too. When he is caught he will have 1 year probation, where he will be subject to random tests, have to attend counselling and will not be at the bottom of every list when a course comes up. If he is caught again they will start looking for ways to convince him to leave the forces, but the penalties will be similar. A third time and he will be discharged. Again this is pretty much how it goes for a recreational user, I have never known anyone who had a trafficking charge, but I highly doubt they will be as lenient.
I am friends with one guy who was charged for use of in illegal substance when we on our QL3 (trade course). The charge has hurt his career, but he has stopped using drugs. It has been 3 years since he was charged and 2 other guys who were charged with them have either quit or been discharged.
Do they take blood/urine samples before a tour? He was hoping to go to Europe for a tour. I can't speak for him though, but I know this would be his third year.
It's good they take steps against drug use, even recreational. Drugs are harder to detect than alcohol, and having someone stoned while they should have all their senses alerted is worrysome.