Number of accidents in commercial operations primarily caused by drug/alcohol intake - 0
Based on this historical evidence the likely number to be prevented in the future - 0
The only positive outcome will be a big promotion for the bright spark who has been riding this horse and cart. Seen it before. Of course as soon as they move on it will be forgotton about, but unfortunately we will be left with a piece of legislation that someone will pull out in 20 years time, blow the dust off, and hang someone with because they had a beer in the hangar after work.
Of course it will be rather simple to get this policy and procedures into your organisation. Simply make it part of your Total Error Management System, above your Safety Management System, next to your Fatigue Management system, adjacent to your Crew Resource Management Training, and just after your Risk Assessment and Control Policy!! Of course your Transport Security Policy has to fit in there as well.
Once you've drafted that lot and trained everyone up - which should take about 12 months - you can finally go flying. But don't have a beer to celebrate that achievement, that's illegal.
As a famous bear once said - Bother!