http://www.insidethegames.biz/olympics/summer-olympics/2016/1016640-australia-introduce-olympic-alcohol-ban-in-order-to-boost-performance-at-rio-2016
They can't drink in the Olympic Village or on the flight home. They can drink outside the village, but have to "drink responsibly".
Pretty embarrassing if you're a professional athlete and your Olympic committee needs to treat you like like a bunch of children going on a class trip.