a tough one

My hubby is off to confront someone near and dear to us about drinking. We have been concerned for a while, along with many other people. But today this person was downtown and hubby pulled the car around. Inside was a can of 7-Up and a glass (a freaking glass) of rum. So we know that this person is drinking and driving (OK I suspected the last... and I do mean last time I got a ride). What do you do? And much of the family is in denial... or simply does not see thru the cover even though they know our concerns.