The main purpose of the SHIELD Act of 2025 is to ensure that federal law enforcement officers who are enforcing immigration laws are not arrested or prosecuted by state or local governments. The act aims to protect these officers while they perform their duties, asserting that immigration enforcement is a federal responsibility. Key provisions of the act include a prohibition on federal funding to any state or local government that arrests, detains, or prosecutes federal law enforcement officers for actions taken in the lawful performance of their immigration enforcement duties.