Every company I have worked for for the last ten years has had a zero tolerance rule. Immediate termination on proof of drug abuse, including alcohol if it affects work or you can smell them from ten feet away.
It has also been enforced. I tell trainees that if they do it on their personal time it is their business. However, if they show up to work messed up I will test them and upon proof, fire them. We also have mandatory drug testing that they have to read about and sign a waiver for. If they pop positive they are out.
There are enough problems, dangers, and liabilities to deal with, without having to worry about if your co-worker is coherent enough to secure power if you get lit up testing high voltage systems.
