WASHINGTON—The Justice Department is suing Walmart, alleging the retail giant unlawfully dispensed controlled substances that fueled the opioid crisis. A civil complaint filed on Dec. 22 alleges Walmart pharmacists knowingly filled thousands of prescriptions for controlled substances that they knew were invalid. The complaint also alleges that Walmart received hundreds of thousands of suspicious orders that it failed to report as required by the Drug Enforcement Administration (DEA). “The complaint lists Florida pill mill doctors who wrote improper prescriptions for thousands of individuals,” Maria Chapa Lopez, U.S. attorney for the Middle District of Florida, told reporters on a conference call. “Some of these pill mill prescribers even told their customers to bring their prescriptions to Walmart to have them filled because other pharmacies would not fill them.” Around 80 percent of all heroin addicts start their habit through prescription painkillers. In 2018, more than 67,000 Americans died of drug overdoses, …