(CN) – A California state appeals court dealt Monsanto a legal defeat on Thursday, ruling the state was well within in its legal bounds when it decided to list a weed-killing chemical as a possible cancer-causing agent.

California’s Fifth Appellate District affirmed a ruling, saying California’s decision to list glyphosate as a possible carcinogen, based on determinations made by international health organizations, did not override the rights of U.S. citizens.

“Fundamentally, appellants’ argument is that a state’s delegation of its lawmaking authority is an inappropriate violation of the republican form of government when that delegation is to a foreign agency,” said a three-judge panel in a 43-page ruling issued on Thursday. “Yet there is no question, given the extensive analysis of the United States Constitution … that the state has authority to delegate legislative authority under long-settled principles consistent with republican forms of government.”

In other words, the Office of Environmental Health and Hazard Assessment (OEHHA) acted appropriately when it listed glyphosate, a weed-killing chemical sold commercially as RoundUp, under the Proposition 65 list of chemicals believed to cause cancer.

“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 California for Food Safety.

Last year, OEHHA listed the widely used weed abatement chemical as a possible carcinogen, citing the findings of the International Agency for Research on Cancer (IARC), a division of the World Health Organization that focuses on researching the lifestyle and environmental risk factors that contribute to cancer rates.

Monsanto asserted that California’s reliance on a foreign entity not beholden to voters in the United States amounted to an end around U.S. sovereignty and sued in Fresno County Superior Court.

Superior Court Judge Kristi Kapetan ruled OEHHA acted legally by relying on international data on cancer when listing the chemical, a judgment affirmed by the panel on Thursday.

Proposition 65, approved by California voters in 1986 as concerns over public health issues such as safe drinking water came to light, requires OEHHA to list all chemical agents with a known association to cancer.

In 2015, a 17-person scientific panel appointed by the IARC, concluded that glyphosate was a probable carcinogen for humans, the first time any major health regulatory body acknowledged a link between the widely used herbicide and cancer.

Monsanto, a chemical manufacturer which is expected to merge with drug manufacturer Bayer after the Trump administration approved the corporate consolidation on Thursday, has maintained glyphosate and its commercial applications are safe for human use.

The court’s ruling has no bearing on the safety of the chemical, only the ability of state agencies such as OEHHA to use determinations made by foreign organizations as support in decision-making processes.

Monsanto said in a statement, “More than 800 scientific studies, the U.S. EPA and the National Institutes of Health have determined that glyphosate is safe for use and does not cause cancer, and a U.S. federal court judge has already ruled on constitutional grounds that Prop 65 warning requirements for glyphosate would be misleading. We are reviewing today’s ruling by the state court of appeals and will be analyzing further options. Meanwhile, we continue to stand with the broad agricultural coalition that has successfully brought a separate legal challenge of the Prop 65 listing in federal court.”