SPRINGFIELD — The state’s top legal officer is putting his weight behind an Illinois law that prevents state and local law enforcement from acting on behalf of federal immigration authorities.Illinois Attorney General Kwame Y. Raoul filed an amicus brief Tuesday with the U.S. District Court for the Northern District of Illinois defending the constitutionality of the TRUST Act in a lawsuit against the Stephenson County Sheriff’s Office.That case is Pedro Tlapa Castillo v. David Snyders, No. 19 C 50311 …