The STOP Nitazenes Act permanently schedules nitazenes (a class of synthetic opioids chemically known as 2-benzylbenzimidazole opioids) as Schedule I controlled substances under federal law, making them illegal to manufacture, possess, or distribute. The bill targets specific nitazene drugs like etonitazene and metonitazene, which have emerged as dangerous street drugs, as well as any chemically similar compounds that activate opioid receptors in the brain. Any nitazenes that were previously placed on a temporary schedule automatically become permanently scheduled upon the bill's enactment. The Attorney General must issue implementation rules within one year of the law taking effect, which can initially be issued as interim rules that take effect immediately while the public provides feedback before final rules are finalized. This legislation affects drug manufacturers, distributors, law enforcement, and public health officials working to combat the opioid crisis.