Rule 17. Each party to the conflict must take all feasible precautions in the choice of means and methods of warfare with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects.
State practice establishes this rule as a norm of customary international law applicable in international and non-international armed conflicts. This rule must be applied independently of the simultaneous application of the principle of proportionality (see Rule 14).
The duty to take all feasible precautions in the choice of means and methods of warfare is set forth in Article 57(2)(a)(ii) of Additional Protocol I, to which no relevant reservations have been made.
This obligation is included in numerous military manuals.
It is also supported by official statements and reported practice.
This practice includes that of States not, or not at the time, party to Additional Protocol I.
When the ICRC appealed to the parties to the conflict in the Middle East in October 1973, i.e., before the adoption of Additional Protocol I, to take all feasible precautions in the choice of means and methods of warfare, the States concerned (Egypt, Iraq, Israel and Syrian Arab Republic) replied favourably.
While Additional Protocol II does not include an explicit reference to the obligation to take all feasible precautions in the choice of means and methods of warfare, more recent treaty law applicable in non-international armed conflicts does so, namely the Second Protocol to the Hague Convention for the Protection of Cultural Property.
In addition, this rule is contained in other instruments pertaining also to non-international armed conflicts.
This rule is set forth in military manuals which are applicable in or have been applied in non-international armed conflicts.
The jurisprudence of the International Criminal Tribunal for the Former Yugoslavia and of the European Court of Human Rights provides further evidence of the customary nature of this rule in both international and non-international armed conflicts.
In its judgment in the Kupreškić case
, the International Criminal Tribunal for the Former Yugoslavia considered that this rule was customary because it specified and fleshed out general pre-existing norms.
It can be argued indeed that the principle of distinction, which is customary in international and non-international armed conflicts, inherently requires respect for this rule. The Tribunal also relied on the fact that this rule had not been contested by any State.
This study found no official contrary practice either.
Examples of the application of this rule include considerations about the timing of attacks, avoiding combat in populated areas, the selection of means of warfare proportionate to the target, the use of precision weapons and target selection. In addition, Rule 21 sets out a specific requirement with respect to target selection.