Lil Wayne's Dry Tour

A rep for the I Am Still Music Tour tells TMZ, the concerts have "a dry backstage as we are committed to keeping a safe and professional atmosphere to ensure a smoothly running tour."

But that doesn't mean the audience can't drink -- according to the rep, the no-alcohol policy only extends backstage ... "there is no ban on alcohol served at the venues."

Weezy is forbidden from drinking alcohol as part of his three-year probation, which kicked off last year -- following a drug-filled tour bus incident back in 2008.