A sharply divided Iowa Supreme Court on Friday stopped a lawsuit aimed at reducing the flow of fertilizer and hog farm waste into the state’s river and streams, finding that limiting pollution from farms was a political matter and not one for the courts.

The 4-3 decision handed a significant defeat to environmental groups hoping to get the chance to prove that Iowa should scrap it’s voluntary farm pollution policy, order new mandatory limits on nitrogen and phosphorous pollution and stop construction of new hog barns.

It is the latest court rejection of an attempt to force the nation’s leading corn and pork producing state to clean up farm pollutants from its major rivers that provide drinking water to hundreds of thousands of Iowans.

The lawsuit, which was brought by Iowa Citizens for Community Improvement and Food & Water Watch, contended that unregulated farm pollution is violating the rights of citizens to clean water in the Raccoon River for recreational and drinking water use.

It said a legal concept that precedes Iowa statehood — the public trust doctrine — should apply to this case and require the state to ensure that citizens have a useable Raccoon River untainted by excess pollution caused by farm runoff of fertilizer and animal manure.

A state judge ruled in 2019 that the environmental groups sufficiently demonstrated that they suffered injury because the river’s untreated water is too polluted to enjoy recreationally or aesthetically. The state appealed the ruling and asked the court to dismiss the lawsuit.

Four of the court’s conservative justices said the environmental groups didn’t show that the state’s actions had caused a concrete injury the courts could fix. They also said the public trust doctrine historically hasn’t been used to solve a problem as complex as the environmental issues raised, and that the issues at the heart of the case were political questions that would fall to the Legislature to settle.

“There is not enough here to demonstrate that a favorable outcome in this case is likely to redress the plaintiffs’ alleged reduced ability to kayak, swim, or enjoy views of the Raccoon River, or would save them money on drinking water. The plaintiffs’ claims must therefore be dismissed for lack of standing,” Justice Edward Mansfield wrote for the majority.