In a development heralded as "a win for science and democracy" and for "all Californians," an appeals court on Thursday backed the state's listing of glyphosate, the active ingredient in Monsanto's Roundup, as a probable carcinogen.

"This is a huge win for all Californians—and a huge loss for Monsanto—as it upholds our right to protect ourselves and our environment from unnecessary and unwanted exposure to the dangerous chemical, glyphosate," said Adam Keats, senior attorney at the Center for Food Safety (CFS).

Following the the World Health Organization's International Agency for Research on Cancer (IARC) 2015 listing of glyphosate as a probable carcinogen, California's Office of Environmental Health Hazard Assessment (OEHHA) announced that, in adherence with its Proposition 65, it planned on listing glyphosate as a chemical known to the state to cause cancer, citing the IARC research. That listing would require warning labels on packages.

Monsanto promptly sued the state over the move, and CFS intervened in the case to defend the listing and accused the agribusiness giant of "trying to keep the public in the dark about potential hazards from their products." Other labor rights and environmental groups including the Natural Resources Defense Council (NRDC) also intervened to support the listing.

Though Monsanto had argued that basing the designation on the IARC's conclusions was improper because the research body is a foreign entity, California's 5th District Court of Appeal rebuffed that argument.

The ruling says that "there is no question... that the state has authority to delegate legislative authority under long-settled principles consistent with republican forms of government." It goes on to say that the "appellants provide us with no reason or analysis why the United States' guarantee to states that they shall enjoy a republican form of government should provide appellants with an individual right to challenge a state's authority to enact its own laws."

Rebecca Riley, senior attorney with NRDC, also applauded the court's affirmation, calling it "a win for science and democracy."

"Monsanto doesn't get to tell California how to protect its people from dangerous chemicals or how to run the Prop 65 list," she said. "The ruling clearly backs the voters' choice to rely on expert scientific bodies to add dangerous chemicals to its list."