Observers packed a federal courtroom in downtown Honolulu on Wednesday to watch attorneys for several of the world’s agricultural giants and opponents of genetically engineered farming battle over three county laws that target GMO crops and pesticide use.

Three judges from the 9th U.S. Circuit Court of Appeals heard oral arguments from both sides of the debate for about three hours, while both supporters and opponents of the county laws watched intensely from seats in the courtroom and in two rooms set up with television monitors for the overflow.

Biotech companies, including Syngenta and Monsanto, and multiple local groups sued the neighbor island counties over passage of the laws, winning all three of the cases in federal court in Honolulu.

The counties, environmental groups and GMO opponents are asking the 9th Circuit to overturn the decisions. Some of the major groups defending the county laws include the Center for Food Safety and Earthjustice. Parties to the proceedings also include Pesticide Action Network North America, SHAKA and Surfrider Foundation.

In 2013, the Kauai County Council passed a law that could lead to prison time and stiff fines for employees of large agricultural companies if they don’t divulge information about pesticide use, abide by setback rules for spraying pesticides, or disclose specifics about genetically engineered crops.

Shortly thereafter, Hawaii island Mayor Billy Kenoi signed a bill into law prohibiting biotech companies from operating on the island and banning farmers from growing any new genetically altered crops. The law exempted the island’s GMO papaya industry.

In 2014, Maui County voters approved a ballot initiative that prohibited testing and cultivation of genetically altered crops until an environmental and public health study is conducted that finds the agricultural practices safe.

While the laws differ, the fundamental legal issue pervading all three of the court cases is whether the counties overstepped their bounds and pre-empted state and federal authority to regulate agricultural crops and pesticides.

A parade of top Honolulu and mainland attorneys focused on that issue for most of their oral arguments. Each party was allocated 15 minutes to make its case, which was often extended as the judges peppered them with questions and poked holes in their arguments.

Paul Achitoff, an attorney for Earthjustice, an environmental law firm in Honolulu representing various parties in the court cases, has been an early and strong supporter of the county laws restricting the GMO industry and pesticides. He consistently argued that the counties have power to oversee agriculture and pesticides as long as rules and restrictions don’t conflict with state regulations.

“First of all, there is no state policy, or law or regulation that gives anybody a right to grow whatever they want, wherever they want, whenever they want. There is no such right, there is no state policy,” he told the court in regard to arguments relating to the Kauai County case. “You are correct that the (state) Department of Agriculture has the authority to designate or restrict harmful plants. The question here is, is that authority exclusive? Certainly the Department of Agriculture has broad authority, but broad authority isn’t the same as exclusive authority.”

Attorneys for parties supporting the county laws also argued that federal and state agencies had failed in certain cases to adequately regulate GMO crops and pesticides, necessitating counties to exercise their police power to protect public health.

However, attorneys for the biotech companies consistently argued throughout the case hearings that the counties don’t have the authority to regulate genetically engineered crops or pesticides, which is the purview of multiple federal and state agencies.

“The issue in this case isn’t whether pesticides and GE (genetically engineered) plants should be regulated or what those regulations should be,” said Christopher Landau, who is representing the biotech industry. “The only question here is, ‘Who does the regulation?’ Under current Hawaii law the answer to that question is clear: It is the state, not the individual counties.”

Margery Bronster, a former Hawaii attorney general who is representing the biotech industry and local farming associations, also emphasized to the court that Hawaii has generally delegated very limited powers to the counties.

“Hawaii is an incredibly centralized government. We have no townships, we have no towns. We have the state government, which covers everything and we’ve got the four counties,” she told the court. “Historically, we have not delegated tremendous regulatory authority to the counties.”

Parties to the proceedings estimate that the court will issue rulings in each of the three cases in roughly three to nine months.