"METAIRIE, La. -- Business was brisk at Bayou Daiquiri's drive-through window on a recent Friday night, as cars lined up four deep to buy vodka-laced frozen drinks in 32 flavors. A young woman with two children in the back seat bought a large strawberry margarita in a styrofoam cup, then weaved one-handed back onto the busy highway.

"She can thank George Brown, executive director of the Beer League of Louisiana, the industry's powerful trade group. A state law passed three years ago forbids drivers to carry open containers of alcohol, but there's a line buried in the law exempting "any amount of frozen alcoholic beverage" in a cup, as long as a straw isn't stuck through the lid. Mr. Brown doesn't mind taking credit. "We did it for one of our friends" in the daiquiri business, he says.

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"Mr. Brown battled the 21-year-old drinking age, which by then was being adopted across the country, and railed against "federal blackmail" when the government began cutting off highway funds to states that failed to comply. Fearing the loss of money, Louisiana's legislature raised the drinking age in 1987. But the Beer lobby won a version that made it illegal for those under 21 to drink but didn't explicitly prohibit the sale of alcohol to those under 21 until 1995.