Treats state and local officials who honor Department of Homeland Security (DHS) immigration detainers as acting for DHS and gives them the same authority and general liability protection as DHS officers, while excluding protection for anyone who knowingly violates civil or constitutional rights. Defines “sanctuary jurisdiction” as a state or locality with a law, policy, or practice that prevents sharing immigration or citizenship information or following DHS detainers, with a limited exception for victims or witnesses. Makes jurisdictions that meet that definition ineligible for specified federal economic and community development grants and requires return/reallocation of funds if a grantee becomes a sanctuary jurisdiction; the grant-eligibility changes take effect October 1, 2025.