Kentucky's Republican-led General Assembly overrode Governor Andy Beshear's veto of a law that could shield Bayer from state lawsuits alleging it failed to warn customers that its Roundup weedkiller could cause cancer. Kentucky became the third state to enact such a legal shield, following North Dakota and Georgia, which passed similar laws last year.

At the heart of most lawsuits against Bayer is the claim that Roundup's manufacturer failed to warn customers of the product's potential cancer risk. The federally approved label for Roundup includes no warning of cancer, and according to the U.S. Environmental Protection Agency, glyphosate is not likely to be carcinogenic to humans when used as directed. Bayer contends that federal pesticide laws preempt state failure-to-warn claims because states cannot require additional labeling beyond federally approved labels.

Bayer partnered with Modern Ag Alliance, a coalition of agricultural organizations, to back bills in multiple states declaring that a federally approved pesticide label satisfies any duty under state law to warn customers. Elizabeth Burns-Thompson, executive director of Modern Ag Alliance, said "Farmers need clear, consistent rules to plan for the future and keep their operations profitable."

Approximately 200,000 claims alleging that glyphosate causes non-Hodgkin lymphoma have been filed against Bayer, and the company has paid more than $10 billion to resolve earlier Roundup-related claims. Bayer disputes assertions that glyphosate causes cancer and has said legal costs from the litigation threaten its ability to continue selling glyphosate-based products in U.S. agricultural markets.

A St. Louis Circuit Court judge gave preliminary approval last month to a proposed settlement to resolve most pending and future failure-to-warn claims involving Roundup. Bayer has asked a Missouri court to approve a $7.25 billion settlement, with the company making annual payments into a special fund for up to 21 years. Under the proposal, an agricultural, industrial or turf worker exposed extensively to Roundup and diagnosed with aggressive non-Hodgkin lymphoma before age 60 would receive an average of $165,000, while people diagnosed at age 78 or older would receive an average of $10,000. Claimants may opt out of the proposed settlement by June 4.

The U.S. Supreme Court is considering the case Monsanto Company v. John L. Durnell, which centers on whether the Federal Insecticide, Fungicide, and Rodenticide Act preempts state-level failure-to-warn claims. The Justice Department filed a brief supporting Monsanto's argument that federal pesticide law preempts such claims, reversing the position of the Biden administration. Sen. Cory Booker filed an amicus brief backing cancer patients in the case.

Monsanto introduced Roundup in 1974 with glyphosate as its active ingredient. Bayer acquired Monsanto in 2018. President Donald Trump has directed federal agencies to boost production of glyphosate, calling it critical to national security and the U.S. food supply. In February, Booker condemned an executive order directing federal agencies to boost glyphosate production.