Former U.S. Attorney Karen Hewitt has turned the tables by suing the U.S. Department of Justice on behalf of Walmart over federal opioid law.

Hewitt, who is now Jones Day’s partner-in-charge of the California region, is the lead counsel in litigation in Texas federal court in which Walmart alleged that the Department of Justice and the U.S. Drug Enforcement Administration are threatening to hold pharmacists and pharmacies liable for violating “unwritten expectations” about how to handle opioid prescriptions.