Under U.S. rules a .02 or higher BAC reading requires removal from duty for 8 hours or until retested below .02. Many, but not all, U.S. carriers have alcohol rules in the Ops manual that are more stringent than FAA or Department of Transportation requirements.
Here's some guidance from United's ALPA folks on how a positive alcohol test might play out on an international layover:
Now let’s suppose that you were not laying over in Phoenix, but instead were in London. And it was not a CSR who smelled alcohol on your breath, but instead at security you dropped your bag while hoisting it up on the belt for the x-ray machine and it fell on your foot. The screener asked you if you are alright, and you exchange pleasantries. 20 minutes later it is the London police who find you in Operations to report that the screener smelled alcohol. The police have a breathalyzer with them. The FARs require that you submit to a breath test by a law enforcement agency, or again, the result will be presumed to be positive.
After the breath test, you are taken to the police station and a doctor is called to administer a blood test. You are then arrested and taken to jail. You are charged with a violation of the Transport Safety Act of 2003, in that you performed activities that are ancillary to aviation functions with an unlawfully high blood alcohol content. You are arrested because you had “reported for duty,” and, as Captain, you flight planned and signed for the aircraft. This could be considered to be preparing to serve as a pilot of an aircraft.
Yours might be a test case, as you were arrested down in Operations – not on board the aircraft as has occurred with a few other foreign pilots in London. But you are clearly over the legal limit, as in the UK the legal limit is .02. Now in addition to the FAA revocation, you are facing criminal prosecution in a foreign country, with the possibility of jail time. ALPA might be able to help you find a criminal defense attorney, but there is little we can do to keep you out of the news. British news outlets pay “stringers” to hang around the courts to pick up juicy stories for them. You get written up in the London tabloids, which in this internet era, means that the local TV station back home will soon find out and reporters will be camped out at your door.
http://ual.alpa.org/LinkClick.aspx?f...%3D&tabid=1159
Unfortunately, U.S. pilots have a lot of experience with alcohol cases in the Isleworth Crown Court.