In a federal form of governance, power is constitutionally divided between a central government and regional governments (states or provinces), each having autonomy in certain areas. 

In a unitary system, all powers are concentrated in the central government, which may delegate authority to local bodies, but can revoke it at any time. 

Pre-emptive rules in criminal justice aim to stop crimes before they occur. These include processes where the state screens citizens through aspects of their public life to estimate their propensity for violence, and takes steps to remove their means of committing violence. Examples include withdrawing permission to purchase a weapon or alcohol from individuals who have shown violent tendencies in school, or increasing surveillance on individuals involved in local altercations.