Armed forces face legal and operational dilemmas in complex situations, and need to determine which bodies of law apply. The legal questions arising from the use of force in armed conflict are not new:
What if armed forces find themselves in situations in which they are faced with both lawful targets and civilians protected against attack? What if civilians demonstrating start being violent? Difficult situations may arise in which the status, function or conduct of a person appearing to pose a threat or disrespecting a military order is not immediately evident, for example when a person approaches a checkpoint, a military installation or an area restricted for military reasons. What are the rules applicable to such situations? In which cases would the use of force fall within the conduct of hostilities paradigm or, by contrast, within that of law enforcement?
Effective determination of the appropriate paradigm has a crucial impact on the humanitarian consequences of an operation and a direct effect on the loss of life and injury to persons. Under the law enforcement paradigm, the rules governing the use of force are more restrictive than under a conduct of hostilities paradigm, and are predicated on the principle of ‘last resort’.
The position of the ICRC on the applicability of human rights law during armed conflict, and especially when it comes to the rules governing the use of force, rests on an important preliminary point; while international humanitarian law (IHL) applies only during armed conflict, international human rights law (IHRL) applies both in peace time and in times of armed conflict.
To shed light on these complex issues, the ICRC organized an expert meeting in 2012 on “The use of force in armed conflicts, Interplay between the conduct of hostilities and law enforcement paradigms.”  Experts from around the globe looked at specific scenarios to identify the line dividing the conduct of hostilities and law enforcement paradigms in situations of armed conflict. The meeting report provided an account of the debates that took place, but did not reflect the views of the ICRC. The ICRC subsequently shared its views on these questions in its 2015 report on “International humanitarian law and the challenges of contemporary armed conflicts.” 
In this report, the ICRC explains that while the conduct of hostilities paradigm allows lethal force to be directed against lawful targets (fighters and civilians directly participating in hostilities) as a first resort, the use of lethal force in law enforcement operations may be employed only as a last resort, subject to strict or absolute necessity, as understood under IHRL. A key requirement of the law-enforcement paradigm is to carefully plan the operation in order to avoid, as much as possible, the use of force.
We also suggest a parallel approach be adopted in the case of the simultaneous presence of lawful targets under the conduct of hostilities paradigm and rioting civilians (who are protected against attack). Soldiers are authorized to use force as a first resort against lawful targets, but not against civilians, even when they pose a threat. Such use of force against civilians must follow a graduated response and comply with the principles of necessity and proportionality as understood under IHRL. However, if it is too difficult to distinguish rioting civilians from fighters and/ or civilians directly participating in hostilities, it might be appropriate to deal with the entire situation under law enforcement, and apply an escalation of force procedure with respect to all persons posing a threat.
Result of this reasoning?
To be clear, if a civilian demonstration in a situation of armed conflict turns violent, a resort to force would be governed by law enforcement rules, by the principles of necessity and proportionality as understood under IHRL. In the case of a person approaching an area restricted for military reasons, where it could prove difficult to assess his/her status and the level of threat, the ICRC submits that an escalation of force procedure must be applied, the legal source of which would be the principle of necessity under IHRL. This is valid when the person is a civilian who poses a threat and also in case of doubt as to whether such a person would be a lawful target (where the ICRC considers that he/she must be presumed to be protected against attack).