The OP brings up a serious issue that is bedeviling pretty much every employer (and service industry). I think it is safe to assume that cannabis consumption by employees is already covered in the employee manuals. It doesn't matter whether intoxicants are "legal" or not, employer can still prohibit being "under the influence" - and in safety sensitive roles they have the ability to conduct random drug testing as well as post-incident testing.

Sometime between now and October 17th, AC will change their rules to prohibit the consumption of cannabis onboard (people with "prescriptions" do present a special problem and it is unclear where the government regulations will land on this one). For those who partake prior to departure, they will likely enforce similar rules as alcohol - if you appear impaired, you run the risk of being denied boarding. If you act up during the flight you risk being strapped down and/or the flight gets diverted and the passenger gets handed over to local law enforcement. I suspect they won't allow consumption in the MLL, but if you are discreet about your edibles, it will be pretty hard to enforce (there is a "no outside food rule that already exists).