Legal Cannabis and Safety A good recent development has been the approval of the AS/NZS 4760 standard, which sets out the process for drug testing through saliva. I believe this is more relevant for dealing with cannabis in the workplace as drugs detected in the saliva are going to a far greater indication of impairment compared to a urine test which can show detects for up to 30 days.
As Peter mentioned, the legality is impairment, not legality. The saliva test gives a greater indication of impairment.