Proposition 65 was approved by voters nearly three decades ago and requires store owners to alert consumers of the presence of potentially dangerous chemicals.
Since the passage, disclosure signs have hung from coffee shops, restaurants and other businesses around the state.
While the law has educated the public about exposure to substances that can cause cancer or reproductive harm, the Brown administration said it has also led to frivolous lawsuits.
"Proposition 65 is a good law that's helped many people, but it's being abused by unscrupulous lawyers," Brown said in a statement. "This is an effort to improve the law so it can do what it was intended to do protect Californians from harmful chemicals."
Brown proposed several reforms, including a cap on attorney fees and requiring more proof from plaintiffs who threaten lawsuits.
Any change to Proposition 65 would require a two-thirds vote by the state Legislature. Several lawmakers separately have introduced bills this year aimed at tweaking the law.