A US judge on Wednesday declined to grant preliminary approval for a settlement against Bayer over claims that their Roundup weedkiller causes cancer.

Research first published by a cancer-focused working group formed by the World Health Organization (WHO) in 2015 claimed that glyophosate was “probably carcinogenic to humans.” Although conflicting studies have since been released, including a 10-year-long course of research by the US Environmental Protection Agency, former Roundup producer Monsanto faced an onslaught of lawsuits.

Bayer bought Monsanto in 2018, right before the first verdict came down in favor of a man alleging his non-Hodgkin’s lymphoma was caused by the weedkiller. There have been three similar trials since then, which have resulted in multi-million dollar damage awards for plaintiffs.

In light of these losses, Bayer arranged a class action settlement to prevent future litigation. They sought preliminary approval of the proposed settlement at issue in Wednesday’s decision.

The rejected proposal would have allowed class members to opt-out and sue separately, but they would lose the right to claim punitive damages and would be required to include the opinion of a seven-member science panel on whether Roundup causes cancer. Given the contradicting opinions on this topic, agreeing to such a panel could “undercut the opinions of the plaintiffs’ experts.”

The rejected settlement would have also created a fund shared between Roundup users who had already been diagnosed with non-Hodgkin’s lymphoma and those who had not yet seen signs of the disease. Users without cancer that chose not to opt-out could participate in a medical monitoring program to detect early symptoms, but it would only last for four years. Non-Hodgkin’s lymphoma typically has a latency period of 10-15 years, meaning recent users would likely not experience symptoms while the monitoring program was active.

If class members were diagnosed within that time frame, they could recover compensation from the fund. However, the fund would not have been unlimited and could have been exhausted by claims from consumers who already had cancer diagnoses. Bayer had the option to renew it but was not obligated to. If they chose to end the program prematurely, they would only have to pay a small exit fee.

San Fransisco District Court Judge Vince Chhabria called this arrangement “clearly unreasonable” and for class members that do not currently have cancer. He drew attention to the disproportionate benefit to Monsanto and Bayer at the disadvantage of consumers. He also expressed concern over the likelihood that class members would actually have notice and an opportunity to opt-out and save their chances to sue separately.