The Department of Magical Law Enforcement is the largest department at the Ministry of Magic, although the size of the Department of Mysteries is unknown. Arguably the most important of the various departments, the Department of Magical Law Enforcement is a combination of police and justice facilities and is roughly the equivalent to the Home Office of Muggle Britain.
Misuse of Muggle Artefacts Office
Office for the Detection and Confiscation of Counterfeit Defensive Spells and Protective Objects
Wizengamot Administration Services
Improper Use of Magic