BYO and if you don't bring you don't drink (no sharing). WTF?
while I dont like the idea of kids drinking before 18 either, maybe a beer with dad when they are 16 after a hard days work etc........

anyway I read this to mean if you dont bring your own drinks ou dont drink therefore lets say tom and jack, Toms parents give him drinks but Jacks dont the invite says tom can drink but because Jack didn't bring any he isn't allowed to have any, hence keeping the kids who aren't allowed to drink free from alcohol IYKWIM!!!