WASHINGTON DC - Twenty top US law officers are urging the Federal Trade Commission to limit alcohol ads to media in which only 15% of the audience is aged 12 to 20 in a bid to crackdown on teenage drinking.
   The group of State Attorneys General says current industry voluntary codes, which limit ads to media where no more than 30% of the audience is under 21, do not go far enough and regulations should be mandatory.
   However, Dan Jaffe, evp of the Association of National Advertisers, says: "It's my strong guess that the FTC could not enforce this. It's highly unlikely to be constitutional."