F.U.I
The only issue about what is rules and what is guidelines relates to maintaining your licence versus your job. If you fly under any CAA reg about BAL but your company imposes a more limiting one then that might mean your job but not your licence. Of course they can sack you for things like not wearing your hat if its in the FOM etc...
I personally recommend calling sick when you see the drink tester - assuming you havent signed on.. and most airlines like to keep sign on to a minimum to maximise duty times. seems when some rules suit they push it the way they like and when not push them the other way... If you believe statistics only 40% of road accidents involve alcohol ... so that implies that if you are drunk you are less likely to be in one... if you extended that to flying we would all be safer being hammered..at least until the stats caught up!! (of course tongue in cheek)