The California Supreme Court refused Wednesday to hear a challenge to a key provision of the state’s landmark chemical consumer-disclosure law, Proposition 65, brought by Monsanto. The chemical maker was seeking to force California to remove glyphosate, found in the company’s Roundup products, from the Proposition 65 list of carcinogens.

This decision leaves in place lower court decisions upholding a provision of the voter-approved initiative that allows outside expert scientific findings to be considered when adding chemicals to the public list of carcinogens.

It also follows a landmark verdict last Friday that awarded Mr. Dewayne Johnson $289 Million in damages from Monsanto. It was found that the use of Monsanto’s Roundup weedkiller caused Mr. Johnson to get cancer.

Glyphosate is the most widely used pesticide in the United States and the world. It is also the most widely used pesticide in California, as measured by area of treated land.