Regardless of how the rule is worded, it will still be up to individual members to accept and live up to it, and up to the various club administrations to enforce it and take appropriate action against people dumb enough to violate it.
About blood alcohol levels: When I had a pleasant month of March in 1990 test driving on a frozen lake in Northern Sweden, we were briefed that the limit in Sweden was 0.04%. For me, at at my weight of about 195, that meant slightly more than a beer per hour. The penalty for the first offence was 2 year suspension of driving liscence and a year in jail. Nobody asked what they did for a second conviction. The Swedes claimed this lowered the accident and death rate involving DUI by over 50%. You did not have to actually be driving, either. All you had to do was be caught behind the wheel of a car, or the only occupant of a parked car. They justified it using the numerous clinical studies that measured changes in thought processes, reflexes, and several other factors with subjects drinking various beverages under controlled conditions.