Billy Martin can do them; Reggie Jackson can't. Billy Kilmer can; Joe Theismann can't. Joe Frazier's allowed; Muhammad Ali isn't.

At issue are those palsy-walsy, mock macho beer commercials that Madison Avenue has gotten down to such a fine art that they've become one of the most familiar running series in television land. All the jocks you see in them are either retired or safely ensconced in the managerial ranks.

That's because for the past 27 years, the federal government has prohibited active professional athletes from appearing in commercials for alcoholic beverages.

The idea behind the ban is that athletes are the objects of vast hero-worship, and that depicting any but an over-the-hill member of the species with beer in hand might mislead the nation's youth into thinking that if they drink his brand they, too, can kick a 55-yard field goal.

The athletes, it goes without saying, find that logic faulty. Yesterday they sent one of their lawyers to plead their case before officials of the Treausury Department's Bureau of Alcohol, Tobacco and Firearms. Three years after it announced it would review all labeling and advertising regulations for beer, wine and distilled spirits, the bureau has just now arrived at the public hearing stage of the process.

"The average playing career in the NFL is 4.6 years," Richard Berthelsen, counsel to the National Football League Players Association, told the six-member hearing panel. "That means that the opportunity to exploit one's name commercially is confined to a short period of time." He went on to cite numerous court cases that protect the rights of a celebrity to exploit his name.

He also argued that the public makes little or no distinctions between active and retired athletes, nor, for that matter, are children any more susceptible to the claims of athletes than they are to those of, say, rock stars, who are not covered by the ban.

The six-member panel listened appreciatively, but appeared unlikely to lift the ban on active athletes. Still, it seemed troubled by the knotty question of who qualifies as "active." Whither, for example, Ali?

Berthelsen picked up little support yesterday from the brewers. Most were happy to leave that portion of the proposed regs alone. In fact, one brewer, the Joseph Schlitz Brewing Co., wanted to go the feds one better by banning ex-jocks and managers as well.

"The prohibition is most appropriate, but it's too limited," said Daniel T. Coughlin, a vice president of Schlitz. "It begs reality. The popularity of athletes extends well beyond their active, playing years."

Schlitz does not use ex-jocks in its advertising campaign, while its toughest competitor, Miller, maintains a huge and growing stable, featured in its well-known campaign for Miller Lite. "My position could be interpreted as self-serving, but that really isn't it at all," Coughlin said.

Whether they're willing to admit it or not -- and many are not as bashful as the man from Schlitz --each brewer was out yesterday to use the regulatory process to help him protect his competitive edge in the marketplace.

The best example came in the squabble over the use of the term "natural" in beer labels. The proposed regs call for the word to apply only when a product meets a number of criteria, including being only "minimally processed."

Anheuser-Busch Inc. was horrified. The basic ingrediants of beer, it noted in written comments, are "milled, mashed, strained, boiled, flavored with hops, cooled, charged with yeast, fermented, chill-proofed, blended with carbonated water, filtered, packaged and pasteurized." Obviously, it fretted, not minimally processed.

The company argued that its popular brand, Natural Light, would be totally destroyed if the regulations went into effect. At the very least, it asked that brands that currently use the term "natural" should be protected by a grandfather clause.

No way, retorted Miller, which has been fighting the natural issue in various forums for years. There's no such thing as a natural beer, Miller claimed in written testimony, adding helpfully that any company that has marketed such a beer should be forced to conduct a massive remedial ad campaign to confess past deceptions.

The battle will continue at more hearings on the West Coast later this year. The regulatory review, already three years old, is barely past the halfway point.