Thanks to a group of activist wine connoisseurs who filed a suit in U.S. court, there may soon be more body to the labels on the bottle of American wine.

Applying truth-in-labeling requirements, U.S. District Judge Gerhard A. Gesell ruled yesterday that American wine bottle labels must tell the minimum percentage of certain grape varieties in the bottle their geographic origin and the company that produced the wine.

Gesell's decision came in a suit brought by three persons he identified as "sophisticated wine consumers who were challenging new labeling regulations by the Treasury Department's Bureau of Alcohol, Tobacco and Firearms. Gesel said that the regulations would have to be rewritten to require that information.

The government had argued that such information was unnecessarily costly and would "clutter" wine labels. It said it planned instead to educate consumers on the minimum standards for grape content of certain wines. But Gesell said that such a "public education program" is no substitute for accurate labeling requirements.

The focus of Gesell's ruling was the so-called "varietal rule" that allows wine labels to carry the name of a single game type or variety without disclosing that other, possibly inferior, grape varieties may represent up to 25 percent of the volume.

Varietal wines are those such as "Chardonnay" or "Pinot Noir," which are named after the variety of grape used to make them. Wines that bear more general names, such as "Chablis" or "Burgundy," have no requirements for the minimum percentage of the grapes they contain.

The three wines consumers who challenged the regulations -- a California professor who teaches "enology" or the science of wine, a law professor who is a columnist on wine for the American Bar Association Journal, and an active wine taster -- did not claim that varietal wines must contain 100 percent of the grape variety. They contended, however, that the labels would be "incomplete and misleading," if they did not contain more information.

The consumer also challenged regulations that allow wines to be labeled as coming from one region -- such as Napa Valley or Sonoma Valley, Calif. -- when as much as 25 percent of the grapes may come from elsewhere. Another challenged regulation allowed wineries to suggest they "produced" or "made" a wine when they really received the wine from another winery and only gave it cursory handling before labeling it as their own.

The Treasury Department said its regulations should be accepted because they were based on wine labeling legislation that had been on the books for more than 40 years.

Gesell disagreed. He said, "The clear implication of a label bearing only 'Chardonnay' is that the wine is made fomr the Chardonnay variety grape and no other." He pointed out that the back of such labels sometimes "discourses at length on the virtues of the identified grape type" while failing to mention that the bottle contains a good percentage of another grape.

The U.S. government has had wine-labeling requirements since 1935. The regulations set aside yesterday were approved 15 months ago after three sets of public hearings here and in San Francisco.

The new regulations only made minor alternations in labeling requirements despite 24 volumes' worth of testimony taken from "vineyard owners, wine distrubutors, public officials responsible for consumer protection, geneal consumer advocates, sophisticated wine connoisseurs, and the man in the street," Gesell said.

Gesell noted in his opinion that the type of grape in a wine directly influences its color, fragrance, flavor and other properties. Varietal wines usually cost more than one-varietal wines, he added.

Terms on wine labels cannot be used "in a way likely to deceive or confuse the ordinary consumer," Gesell said in a written opinion. "By assigning inaccurate and undisclosed meanings to words which are otherwise clear and unequivocal, the challenged regulation sanctions the transmittal of false and misleading information."

He said there is "thus no basis, in law or in fact, for permitting the use of a varietal name on wine labels without disclosing that the identified grape variety does not represent 100 percent of the content." He said the same principle applies to the use of geographical origins on wine labels and the description of winemaking operations.

"Congress has directed that wine labeling terminology be understandable to the ordinary consumer," Gesell said. The regulation must be rewritten, he said, to require at least the description of the minimum allowable amount of a specific grape in a varietal wine.

Gesell rejected a further argument by the wine consumers that labels be even more specific and describe each variety of grape used and its origin.

He said such a requirement would be too costly and "prove more a distraction than a benefit," and that most consumers would oppose paying higher prices for "information of marginal value to all but the most sophisticated."

Gesell gave the federal government until next April 30 to rewrite the regulations.