Stop Arming Cartels Act of 2023

This bill bans the private possession, sale, or transfer of rifles capable of firing .50 caliber ammunition, with exceptions for government use and rifles lawfully owned before the law's enactment. It requires owners of such rifles to register them with the National Firearms Registry within 12 months (without fees), and adds these rifles to existing federal firearm reporting requirements. The bill also expands restrictions to prevent firearms from reaching foreign narcotics traffickers designated under the Foreign Narcotics Kingpin Act and modifies legal protections for gun sellers who knowingly supply prohibited weapons.