Stopping Illicit Oil Shipments Act of 2023

This bill requires maritime insurers to verify a vessel's true flag registration before issuing coverage, making failure to do so a material misrepresentation that voids the insurance contract. It directly affects insurers, shipping companies, and sanctioned nations (like Iran and Russia) that rely on false-flag operations to evade oil sanctions. Key mechanisms include state insurance regulators reporting suspicious policies to the Treasury Department, which can then trigger sanctions enforcement actions. The bill aims to disrupt illicit oil trade by cutting off a critical insurance lifeline for sanctioned vessels.