Complex sentence: The Government dictated that the roles of the police would still to keep law and order, but in times of emergency they were also to have an offensive capability assisting the Armed Forces.
Split into simpler sentences: The Government dictated that the roles of the police would still be to maintain law and order, even in times of emergency. However, despite the police not being a combatant force, in times of warfare they were to have an offensive capability assisting the Armed Forces.