JTK,
So many posts and so few actual answers to your question! Unfortunately this post will be of limited assistance too!
The rule will be stipulated in their version of the Aviation Regulations, but of course different countries, different documents!
The USA, for example, is governed by FAR 91.17
Alcohol or drugs.
(a) No person may act or attempt to act as a crewmember of a civil aircraft--
(1) Within 8 hours after the consumption of any alcoholic beverage;
(2) While under the influence of alcohol;
(3) While using any drug that affects the person's faculties in any way contrary to safety; or
[(4) While having an alcohol concentration of 0.04 or greater in a blood or breath specimen. Alcohol concentration means grams of alcohol per deciliter of blood or grams of alcohol per 210 liters of breath.]
Australia has a similar section in their "CAR/CASR"'s.
Good luck finding them!