The future of the Chesapeake Bay looks a little cleaner Monday, after a federal appeals court struck down a case that sought to undermine an effort to clean up the bay.

The Third Circuit Court of Appeals’ newly-released opinion upholds a decision made by a lower court that found that the Environmental Protection Agency-led cleanup effort, which involves all six states in the Chesapeake Bay watershed, is legal. The plan, called the Chesapeake Bay Clean Water Blueprint, establishes a Total Maximum Daily Load (TMDL) for how much nitrogen, phosphorus and sediment can enter the bay each year — limits that aim to cut these forms of pollution by 20-25 percent by 2025.

The EPA’s plan is being put in place by the states in the Chesapeake Bay watershed. But a range of agriculture groups, including the American Farm Bureau Federation, the Fertilizer Institute, and the National Pork Producers Council, have taken issue with the plan, with the Farm Bureau suing the EPA over it in 2011. That lawsuit garnered the support of 21 attorneys general from states almost exclusively outside the Chesapeake Bay region, who claimed that the rule constituted EPA overreach.

Their arguments, however, didn’t stand up in the appeals court. The court’s opinion made clear that the EPA’s regulation of nutrient pollution in the Chesapeake Bay under the Clean Water Act was valid, and that the Farm Bureau’s arguments against the plan were “unpersuasive.”

“Congress made a judgement in the Clean Water Act that the states and the EPA could, working together, best allocate the benefits and burdens of lowering pollution,” the court opinion reads. “The Chesapeake Bay TMDL will require sacrifice by many, but that is a consequence of the tremendous effort it will take to restore health to the Bay…a goal our elected representatives have repeatedly endorsed.”

As the court opinion points out, the Chesapeake Bay has been plagued by this nutrient and sediment pollution — the majority of which comes from farms in the region — for decades. This pollution causes “dead zones” — oxygen-free areas of the Bay that kill clams and worms, key food sources for the region’s iconic blue crabs — and algal blooms that can be toxic to wildlife and humans. The TMDL, which was created at the request of the six Chesapeake Bay states and the District of Columbia after numerous other attempts to clean up the bay failed, puts the states in the watershed on a “pollution diet,” but gives the states flexibility on how to reach reduction targets.

But the Farm Bureau has argued against the TMDL over the last few years partly because it thinks that the plan “eliminates state flexibility to make their own cleanup decisions, or to modify their plans based on new technologies or new information.” That’s something that the Chesapeake Bay Foundation — a defendant in the case — and the EPA dispute.

“Nothing in the TMDL dictates that agriculture do anything one way or another — much less that any kind of zoning occur that is not supported by local government,” Chesapeake Bay Foundation President William Baker said last year. “States and local governments worked together with a number of federal agencies to develop this Clean Water Blueprint for the bay. It’s hardly a mandate being imposed on high down to the states.”

The agriculture groups, along with the 21 Attorneys General, also worried that the plan could set the stage for similar EPA action to clean up watersheds like the Mississippi — a river that cuts through prime agricultural regions.

The Chesapeake Bay Foundation praised the appeals court’s decision.

“This is a great day for everyone who cares about clean water and the Chesapeake Bay,” Baker said in a statement. “In a case challenging EPA’s Clean Water Act authorities, the Third Circuit Court in Philadelphia has spoken.”

Baker said on a press call Monday that the group hoped the Farm Bureau and other opponents of the TMDL would drop their legal opposition to the plan. Opponents could still petition the third circuit’s decision, or try to take the case to the Supreme Court.

A peer-reviewed report published last October found that, on top of the environmental benefits of the TMDL, the cleanup plan would also result in billions of dollars in economic benefits for the region. But not all states in the region are on track to meet the reductions laid out by the plan — Maryland and Virginia are, in general, making progress towards cleaning up their Chesapeake Bay tributaries, but Pennsylvania is “falling dangerously short” of meeting its commitments, the Chesapeake Bay Foundation reported earlier this year. Baker said on the press call that his organization will “continue to call” for accelerated efforts to implement the TMDL in the region.