- Regardless of how old you look, they would always need to ask you for your drinking license. (Granted, this might result in everyone getting ugly "bracelets" when they enter a club, or in non-licensed drinkers not being allowed into that club.)
- Revoking your drinking license would be an excellent deterrent for a lot of crimes, thus freeing up jails, etc. Drunk & disorderly? 1 month suspension. Drunk driving? Not only do you lose your driver's license, you also lose your license to drink. Naturally, drinking without a license (meaning you never got one or had it revoked, not meaning you left it at home), would require stiffer penalties.
This same idea could be extended to other controlled substances. Do you think this would be a good idea? If not, why? Either way, what other side effects would you predict? (Note: I already know it'll never happen.)