Complex sentence: Based on the Justice Department report on discriminatory policing practices within the MCSO, on December 15,2011, the United States Department of Homeland Security revoked the MCSO's federal authority (under 287 (g)) to identify and detain illegal immigrants.
Split into simpler sentences: Based on the Justice Department report on discriminatory policing practices within the MCSO, on December 15,2011, the United States Department of Homeland Security removed the MCSO from the 287 (g) program. This decision revoked the MCSO's federal authority to identify and detain illegal immigrants.