A coalition of patient advocacy groups is urging a federal court to halt the practices of third-party companies that buy drugs from countries outside the FDA-regulated U.S. supply chain, which the groups argue put U.S. patients’ health at risk.

The court filing comes in the wake of a CNBC investigation that documented how these third-parties — commonly referred to as alternative funding programs, or AFPs — have spread across employer-sponsored health plans nationwide. Under the growing business model, AFPs source high-cost specialty drugs from abroad at lower prices and charge employers a fee or a percentage of the savings. The AFPs then provide the medication to patients at little or no cost.

AFPs are especially appealing to small employers like local school districts, county governments and others who pay their staff’s health-care costs out of pocket. But there’s a trade off: Federal officials at the U.S. Department of Homeland Security and the Food and Drug Administration told CNBC that these medications are illegally imported and put patients’ lives at risk. A Homeland Security Investigations official last year told CNBC that criminal investigations into AFPs were ongoing.

The filing in a U.S. Court of Appeals in Maryland, dated Dec. 26, was led by the HIV+Hepatitis Policy Institute, a nonprofit that advocates for safe and affordable treatment for people living with HIV and viral hepatitis.