That delegation of authority needs to be explicit and accompanied by considerable publicity.
Unofficial policy needs to be "don't ask, don't tell" with respect to actions of the volunteers. Quite bluntly, the volunteers are going to kill people under "rules-of-engagement" that are not permitted to the Army or the Police. Authorities must extremely reluctant to look into such incidents and even more reluctant to prosecute.
Volunteers will eventually get into trouble and be outnumbered by enemy forces. When they call for help, the Army should come running in. Questions can be asked later and in private.
Some volunteers will be loose cannons, and must be sent home (or even quietly arrested and prosecuted). There must be arrangements in place to deal with this.
You want effective volunteers - this is how you get them and keep them.
The official rules-of-engagement for the Army and Police need to be explicit and lenient on use-of-lethal-force. Essentially, the commanders must be authorized to order armed hostiles killed on sight and without warning. They should be authorized to order unarmed hostiles killed after repeated clear warnings and failure to disburse. They should be authorized to conduct cross-border raids in some conditions. Collateral damage, injuries, or deaths of "non-combatants" should be a secondary consideration.
Journalists in the area should be treated as probable spies and saboteurs. Their movements should be restricted (by arrest if necessary).
This is War. Treat it as War. Win it decisively.
Not going to happen.