The problem is that with a limit of 9mg/100ml, it is not too difficult to be close to the limit on an early report if you have been out for dinner and a few drinks the night before. Metabolism, stomach contents etc all affect the rate at which you can clear the alcohol from the system. We all have a responsibility to be fit to fly but the company doesn't have the right to stop me drinking in my time off. They do however have a right to expect me to pitch up at work with less than the legal limit but it woul be nice to be able to assess what that limit was. Pilot unions have long been calling for some system to give crews an indication of what their levels might be, without it turning into a witch-hunt.