Stroll the streets of Paris, and it’s easy to see that natural wine is a growing phenomenon. Natural wine fairs have drawn big crowds, and wine bars and shops carrying only natural wines have proliferated, with enthusiastic support from sommeliers, Millennials and urban professionals—the customers many winemakers pay big bucks to ad agencies in hopes of attracting.

But now the French government is asking a question that the natural-wine movement has never answered: What does "natural" mean?

“What does the consumer perceive with regard to these words?” asked Eric Rosaz, manager of the wine sector for the INAO, the French authority that oversees the country’s more than 350 wine appellations. “Is it the same thing as the winemaker? Can we codify the word 'nature' or 'natural'? Should we?”

The natural-wine movement promotes a philosophy that appeals to a growing number of consumers and restaurateurs looking for small-batch drinks produced in a traditional, artisanal manner. It embraces an agrarian ideal. But there is no legal definition for natural wine, nor even a definition agreed upon by proponents. It is entirely unregulated. The lack of certification or legally enforceable standards means consumers have no guarantee that one wine is any more "natural" than the next.

The INAO first entered this debate in December 2014, not at the behest of natural wine producers, but of French organic wine producers, some of whom worry that their place in the market is being unfairly usurped. Organic vintners meet strict certification standards for both farming and winemaking, and they are not happy that they could be losing customers to an undefined category. “For the [organic producers], the concern is that this could lead to the segmentation of the organic wine market,” Rosaz told Wine Spectator.

It certainly complicates things for the consumer, according to Gwénaëlle Le Guillou, director of the Syndicate des Vignerons Bio d’Aquitaine (SVBA). “We have a market for organic wine that remains small in volume. Now we’re going to add another segment with natural wine?” she said. “It means two communication strategies. But the big task for us is to ensure that the wines are organic to begin with, and that is not the case today. You can grow grapes using conventional farming and use little or no [additives] and still call your wine ‘natural,’ because nothing is regulated. It’s confusing for consumers.”

Certified organic French wine allows for the use of copper, sulfur dioxide and vine treatments made from vegetable and mineral extracts. Biodiversity and animal- or vegetable-based fertilizers are in; weed killers are out. A limited selection of common additives are allowed, but there is a strong commitment to use only the additives necessary for the quality of the wine without modifying the nature of the wine. The permitted levels of sulfur dioxide are 50 percent lower than in conventional red wines, and 20 percent lower in dry white wines.

How do you define an undefined category?

Many would contend that fine wine is inherently unnatural, the result of thousands of years of humans intervening in the business of vines. The natural progression of crushed grapes leads to vinegar. Unpruned vines produce grapes that are of little use to modern vintners. Vine treatments, whether synthetic, organic or homeopathic, are used precisely because they interfere with nature.

As a starting point, INAO members met with leaders of the Association des Vins Naturels (AVN), which represents fewer than 50 growers. AVN members sign a good-behavior charter, agreeing to organic or biodynamic viticulture, using indigenous yeasts, and making no adjustments of acidity or sugar levels in their grape musts. They eschew common additives like enzymes and yeast nutrients, allowed in organic wine. Grapes are picked manually. Reverse osmosis, thermo-vinification and cross-filtration are definite no-no’s.

Both sides report satisfaction with the meeting, but the AVN leadership was worried. “We think the government officials are envisioning something wide in scope,” said AVN spokesperson Jacques Flouzat, a wine merchant in central France. “Some people say they produce natural wine but it’s only 1 percent of their production. The rest isn’t. We don’t want those people in our association.”

That raises another potential pitfall for regulators—How to construct a category if natural winemakers can't even agree with each other on its rules?

“[Natural winemaking is] a utopia that is possible on a small surface, but soon as you have [49 acres] or more, it’s unrealistic,” said Pierre Jancou, a Paris restaurateur. Jancou recently opened Achille, a 25-seat bistro in the 11th arrondissement, and was previously associated with La Cremerie, Racines and Vivant, all enormously popular in the city’s natural-wine scene. And that small production is part of the appeal. “I try to find wines you don’t find everywhere because they are produced in such small volumes that they can’t be distributed everywhere.”

Like many natural-wine promoters, Jancou describes himself as a “non-interventionist to the maximum,” but admits he has no hard and fast rule on sulfites in wine. Sulfites exist naturally in wine, and sulfur dioxide is used to protect wine from harmful bacteria and secondary fermentation. Natural-wine purists eschew the addition of sulfur dioxide, and some natural wines suffer scorn for off-putting aromas as a result.

Other natural-wine producers admit to adding a minimal amount during difficult years. “I try to work without sulfites, but some years a batch might need a little,” said Pierre Beauger, who has 3.7 acres in Auvergne in central France, producing 3,000 bottles of table wine with whimsical names that sell for $35 and up. “I put the amount of sulfites, according to lab analysis, on the label.”

The son of a garlic broker, Beauger worked the 1992 harvest at Matanzas Creek Winery in Sonoma before creating his own vineyard in 2001 with the help of his father. He exports to Japan and in 2017 will have an importer in San Francisco. He is also one of numerous natural-wine producers flying below the government radar. “I’m not certified organic and I’ve never presented my wines for the appellation,” said Beauger.

Understandably, this complicates the task of French regulators—they're not sure who is actually making natural wine. “We don’t have the numbers—neither the number of producers nor the volume produced,” confessed Rosaz.

If not natural, what about raw wine?

In April this year, the INAO’s Scientific and Technical Commission proposed two options: a label from a private organization like Demeter, which certifies biodynamic growers, or a government-controlled regulation. The commission heavily favors the latter as it offers more protection for consumers.

As for what that regulation would entail, after careful consideration, the commission reported that there was no real basis, scientific nor technical, for circumscribing the concept of natural wine. They could find no scientific or technical reason for judging one vinification method more “natural” than another.

Yet despite their misgivings, the commission is now tasked with providing a technical definition, which means answering all the questions on what is allowed in the vineyards and cellars. They have hinted that if France were to continue down this path, regulations for natural wine would be stricter than for organic wine, effectively organic wine vinified without additives. For now, French regulators have loosely embraced the guidelines adhered to by members of AVN as their starting point.

But natural wine producers may not wait to see the results. French bureaucracy moves slowly, and in the meantime, the AVN has begun pursuing the possibility of a private certification label similar to Demeter. Interest from growers in other countries has given them hope of taking AVN global.

And some winemakers and fans have moved on to a new moniker: raw wine. They hope it will prove less controversial. “For me, ‘natural wine’ means nothing. It’s so overused. I like ‘vin vivant’—maybe this is best translated as 'raw wine' in English,” said Jancou. “People denigrate us, but we have the right to love raw wine.”

Raw wine has gained momentum thanks to an artisanal wine fair founded by Isabelle Legeron in London in 2012. It’s mushroomed into a multi-country event, with its first appearance in New York this November. Legeron estimates that 30 percent of Raw Wine Fair’s visitors are from the general public. “They are trendy, young, shop at the local farmer’s market, there is an attention to detail and they are really concerned about what they eat,” said Legeron.

A pragmatist, she supports regulation. “We have to be answerable to something in order to protect consumers and protect growers,” said Legeron. “We want to promote transparency in the industry, raise awareness among consumers. If I want to change the system, I have to work within the system.”

But that system may take a while to catch up. “The subject is fascinating and emotional, and the idea has received quite a lot of reflection,” said Rosaz. “It will be long, sensitive work.”