Sweety, there is so much more to life than drinking and his very life may depend on him never having another drink. Alcohol is a drug and it will trigger the urge to go to his drug of choice.
Most recovering addicts I know, at one time thought they could have a couple of drinks...and they found out the hard way that this was not possible.
Most recovering alcoholics I know, at one time thought they could smoke a little pot...and they found out the hard way that this was not possible.
A life of sobriety can be a wonderful life, there are so many great things to do that have nothing to do with drinking, and you never have to worry about driving when you don't drink at all.
So the answer is no, he risks everything to have just one little drink. A drug is a drug is a drug, even if it wasn't the drug of choice the addictive behaviour and reaction is still there.
Good luck, I hope you can figure out how important this really is.
Hugs