This bill, known as the "Stop Arming Cartels Act of 2025," primarily prohibits the importation, sale, manufacture, transfer, or possession of .50 caliber rifles in or affecting interstate or foreign commerce. Exceptions are made for government use by federal or state entities, and for rifles lawfully possessed on or before the enactment date, which are considered "grandfathered." Owners of these grandfathered rifles must register them with the Secretary within 12 months of the Act's enactment, with no associated fee or tax. These registered firearms will be included under the **National Firearms Act of 1934**, and registration information cannot be used as evidence in criminal proceedings for prior violations. The legislation also amends the **Protection of Lawful Commerce in Arms Act (PLCAA)**, creating an exception to its liability protections. This allows lawsuits against manufacturers or sellers who knowingly sell or transfer firearms, or conspire to do so, with reasonable cause to believe the transaction is prohibited under the Foreign Narcotics Kingpin Designation Act, specifically targeting those who might arm **significant foreign narcotics traffickers**. To further combat illicit firearm trafficking, the bill adds these identified or designated foreign narcotics traffickers to the list of individuals federally prohibited from receiving firearms, with conforming amendments to the **National Instant Criminal Background Check System (NICS)**. Additionally, federal firearms licensees will now be required to report multiple sales of **rifles**, alongside pistols and revolvers, to the same person.