The time consuming process of screening volunteers for a new army and police force has provided a large pool of men that can quickly be formed into a para-military security force. And this is what is going to be done. The volunteers were screened to keep out Baath Party activists and members of Saddam's security services and Islamic radicals. The screening isn't perfect, but the main idea is to make it more difficult for pro-Saddam loyalists to take control of military and police units and repeating the cycle of coups and military rebellions that put the Baath Party on the road to power half a century ago. The para-military units would be organized around men from the towns and neighborhoods being guarded. In effect, it would be built on the old Iraqi army reserve organization. This worked by having the Baath Party keep track of all men with military experience in each neighborhood, and all these men could be rapidly notified and organized into a temporary military unit for an emergency. The problem now is that you cannot use the Baath Party officials, if only because many have fled and the rest are keeping their heads down (in some cases to avoid getting killed by the people they used to torment and exploit.) But new local administrations have been created, so it is possible to recruit and train para-military security troops.
The militia idea was avoided initially because of the fear that this would encourage the establishment of warlords, especially if militias were set up before new court systems could be set up to deal with criminals captured. This sort of thing has caused long range problems in the past, and once the coalition forces are gone, the Iraqis would have to try and deal with any warlords. Thus the original plan was to take the time required to screen, train and organize new police and military forces, as well as judicial systems, courts and prisons. That will still be done, but a hundred thousand or more former Iraqi soldiers and police will be formed into local defense units to provide security. This will free coalition forces to get out of the patrolling business and concentrate on hunting down the Baath Party and al Qaeda terrorists.
The death of Ayatollah Mohammad Baqer al-Hakim has made Iraqis more eager to do something about their own security and well being, and not just complain about it. To capitalize on that, the formation of trained and disciplined police and military forces will be delayed so that para-military security militias can be formed.