The "Stop Dangerous Sanctuary Cities Act" seeks to compel state and local law enforcement agencies to cooperate with federal immigration officials, particularly the Department of Homeland Security (DHS). It establishes that any state or local entity complying with a DHS detainer will be considered an agent of DHS, thereby gaining federal authority for those specific actions. This measure is intended to prevent jurisdictions from adopting policies that hinder federal immigration enforcement efforts. A key provision of the bill offers significant legal protections to state and local officers and jurisdictions that comply with DHS detainers. In legal proceedings challenging such compliance, no liability would lie against the state or political subdivision. Furthermore, the officer involved would be deemed a federal employee acting within the scope of their employment, with the United States government substituted as the defendant, though immunity is not granted for knowing violations of civil or constitutional rights. The legislation defines a "sanctuary jurisdiction" as any state or local government with a policy that prohibits or restricts its entities from sharing immigration status information or complying with DHS detainer requests. An exception is made for policies that protect victims or witnesses of criminal offenses, ensuring they are not deemed sanctuary jurisdictions solely on that basis. To enforce compliance, the bill makes sanctuary jurisdictions ineligible for specific federal funding. This includes various grants from the Economic Development Administration , such as those for public works, planning, and technical assistance. Additionally, sanctuary jurisdictions would lose access to Community Development Block Grants , with provisions for the return and reallocation of funds if a jurisdiction becomes non-compliant while receiving them, effective October 1, 2025.