Walmart Inc said on Thursday it had filed a lawsuit against the federal government, seeking clarity on the roles and legal responsibilities of pharmacists and pharmacies in filling opioid prescriptions.

Walmart said certain officials in the U.S. Justice Department are threatening to sue the retail giant, claiming pharmacists should have refused to fill otherwise valid opioid prescriptions.

“We are bringing this lawsuit because there is no federal law requiring pharmacists to interfere in the doctor-patient relationship to the degree DOJ is demanding,” Walmart, which runs one of the largest pharmacy chains in the country, said in a statement.

Walmart in the lawsuit against the DOJ and the Drug Enforcement Administration (DEA) said the federal authorities are seeking civil penalties related to its alleged failure to submit suspicious order reports and added that this potential move would be “unprecedented.”

The DOJ and the DEA did not immediately respond to a request for comment.

On Wednesday, a West Virginia court ruled that Walmart must turn over information about federal and state investigations into its opioid-related practices to hospitals suing the company for allegedly contributing to the epidemic.

Opioid addiction has claimed roughly 400,000 lives in the United States from 1999 to 2017, according to the U.S. Centers for Disease Control and Prevention.

Critics of the industry said opioid makers hid the addiction and abuse risks of prolonged use from consumers.