As far as the UK is concerned, the new Transport and Railway Safety Act 2003 (or summat like that) spells it all out in law now with (very) stringent limits on alcohol in breath, blood, and piddle for aircrew (and others). I think this just legalises what was already a JAR rule anyway. Plod can take samples if there are grounds to suspect. More details can be found on the HMSO website.