The Trump administration sued Walmart on Tuesday, accusing its pharmacies of not properly screening questionable painkiller prescriptions and filling them, ultimately fueling nationwide addiction.

Why it matters: The major retailer "knowingly filled thousands of controlled substance prescriptions that were not issued for legitimate medical purposes or in the usual course of medical practice," the Justice Department alleges.

The state of play: Walmart's network of 5,000 in-store pharmacies were turned into America's leading supplier of highly addictive painkillers, dating back to 2013, per the Wall Street Journal, which first reported the...