There's really no way they could stop you but you wouldn't make it far as alcohol is a substance that impairs your senses and slows your reactions. Trust me...it would suck all the fun out of drinking. The players from back in the day were like the characters on Mad Men, they just drank all day long...it was part of the culture and they didn't have the literature yet about how harmful it was to you.
It's one thing to play tennis at your club after a few beers...it's goofy and fun. No professional player could do this with any success.
After their match however, the pros can get down! I remember Gaudio talking about the players at one South American tournament...they got wasted every night and he woke up hungover and played some of his best tennis. I think Action Jackson could elaborate a bit more on this.
Andre Agassi wrote about in his book being hungover for a dead rubber DC Tie. He assumed that someone would be subbing in for him because it was dead but there was no one to sub. So he was so hungover he played the match with Oakley sunglasses on the whole time. Oakley ended up sending him a car and bunch of sunglasses after he was photographed and put on the cover of Sports Illustrated with the glasses on. LOL
Marat Safin loved to drink, party and smoke during tennis tournaments. He loved going to the Hopman cup because of the large casino that was nearby the tennis complex/resort. At Hopman in 2005, he showed up to play David Sanguinetti and he had a black eye, bruises on his face and was clearly hungover. He lost 67 76 60 in classic Safin fashion.
Drinking and tennis....goes hand in hand really.