When the Bavarian Purity Law was first declared in 1487, not a single European had stepped on the land above the Marcellus Shale in the Eastern United States. The First Nations of Canada weren’t fighting natural gas pipelines, because as far as natural resources go, the Alberta tar sands were centuries away from being in the picture—as was the internal combustion engine.

Yet the law, the Reinheitsgebot, which strictly dictates the ingredients that can be used in making beer, is giving the powerful German brewing industry historic ammunition against the creeping potential for new natural gas exploration.

Fracking is banned in Germany until 2021, but with Chancellor Angela Merkel and others in the government appearing to be tempted by the country’s significant natural gas reserves, an opposition movement is being built around the national beverage. Because without clean German groundwater, you can’t have German beer.

The original Bavarian Purity Law only allowed for water, barley, and hops to be used in the production of beer; at the time, the mechanics of yeast fermentation, never mind hydraulic fracturing, had yet to be discovered. While turning water into lightly alcoholic beer, the fermentation killing off any dangerous bacteria or pathogens, the process of making beer can’t render groundwater contaminated by drilling safe to drink.

“Beer is a craft that we Germans have learned well, but it relies on nature to provide the products,” Sven Foerster, the owner of Foersters Feine Biere in Berlin, tells Newsweek. “Hops, barley malt, yeast and, most important of all, water. Poison the well and you poison the product. Our beer is part of our life, our national soul.”

And so a rather benign sense of nationalism and a historic law that may, incorrectly, bring Germany’s Nazi past to mind is stirring an environmental movement. Polls show that the beer-loving citizens are on the side of Germany’s 1,300 brewers: Two-thirds of the public opposes fracking, according to an Emnid survey from May 2013.

Fracking has plenty of opponents in the United States, but even the death of cattle on ranches near the Bakken Shale, in North Dakota, doesn’t put natural gas exploration between consumers and the all-American hamburger in such a threatening way as with Germany and its beer. Perhaps if Coors, like its mega-brewery German cousin Becks, became an advocate for clean groundwater in the Rockies, the beer-loving American public might think differently about fracking.