Above Datums,
I hate to say it, but your talking rubbish!
There are strict rules governing drinking prior to things like live armed guard as well as flying. What makes you think that IF cannabis were to be made legal the rules would be any different?
I don't agree with drug taking at all, but one of the things about CDT is that it assumes your guilt and asks you to prove your innocence (or incriminate yourself if you're stupid enough to take drugs), which is totally at odds with the basic premise of U.K (and indeed most other countries) law, which assumes your innocence until you are PROVEN guilty in a court of law! You are also, essentially, under open arrest until you have given a sample!