MADISON, Wis. (AP) — A Wisconsin judge ruled Tuesday that state regulators can force factory farms to obtain permits before they discharge pollutants, ensuring protections continue to apply preemptively for lakes, streams and drinking water.

Calumet County Circuit Judge Carey Reed issued the decision from the bench in a lawsuit brought by factory farm lobbyists, finding the state Department of Natural Resources has clear legal authority to protect the state’s waters.

“This ruling is critical because it preserves the DNR’s ability to address water pollution that can be caused by these facilities, at a time when many surface and groundwaters around the state are contaminated with animal waste,” said Evan Feinauer, an attorney with environmental advocacy group Clean Wisconsin. “Allowing large dairies to sidestep oversight would have been catastrophic for water protection in our state.”

Wisconsin Manufacturers and Commerce, the state’s largest business group, filed a lawsuit in Calumet County in May on behalf of the Wisconsin Dairy Alliance and the Venture Dairy Cooperative, two groups that lobby for factory farms.

The groups challenged the DNR’s authority to impose mandates through factory farms’ water pollution permits such as monitoring groundwater pollution levels, implementing manure management plans and limiting herd sizes. Last year the agency scaled back S&S Jerseyland Dairy’s request to expand from roughly 5,000 cows to 10,000 cows, allowing the operation to add only about 2,400 animals.

The plaintiffs alleged that federal courts in 2005 and 2011 struck down the U.S. Environmental Protection Agency’s authority to require factory farms obtain permits before they actually discharge contaminants into navigable waters. Therefore, the groups argued, the DNR’s requirement that factory farms obtain permits before the fact was also invalid because it now conflicted with federal law.

The groups’ interpretation would have allowed factory farms greater freedom to increase herd sizes and contaminate state waters with chemicals such as nitrates and phosphates from manure and other fertilizers.

Reed sided with the DNR, pointing to a section of state law that declares Wisconsin policy calls for restoring and maintaining the integrity of its waters to protect public health and aquatic wildlife.

WMC spokesperson Nick Novak declined to comment on the ruling.

The farming industry and environmentalists have been locked in a fierce back-and-forth over regulating factory farms, defined as farms with at least 1,000 beef cattle, 715 dairy cows or 200,000 chickens. According to the state Department of Natural Resources, more than 330 such farms are currently permitted to operate in Wisconsin.

Conservationists say factory farms produce massive amounts of manure that contaminate groundwater, streams and creeks. Industry advocates counter that regulations are too strict and stifle growth.

Clean Wisconsin and the Wisconsin Farmers Union, a group that lobbies for sustainable farming, joined the case as intervenors. Environmental law firm Midwest Environmental Advocates represented that group in the proceedings.

“We are pleased that the circuit court upheld longstanding clean water protections and rejected this reckless lawsuit,” Midwest Environmental Advocates staff attorney Adam Voskuil said in a statement. “The claims advanced by Wisconsin Manufacturers and Commerce and their clients would have exposed rural Wisconsinites and small family farmers to illegal manure discharges, polluting their drinking water and Wisconsin’s rivers and lakes.”