Session I 
Ascertaining International Customary Law on the Use of Force: The Role of States 

A) The respective role of practice and opinio juris. 
- What is the nature of practice required in order to establish a customary rule on the use of force? 
- Should one take into account only practice consisting in specific conduct of States? 
- Could one also rely on assertions in abstracto of the existence of a rule? 
- What is the relative weight to be given to practice and opinio juris in determining the existence of a rule? 
- It has been observed that in the Nicaragua and in the Nuclear Weapons cases the ICJ primarily looked at the existence of the opinio juris of States, as expressed in treaties and General Assembly resolutions, instead of examining State practice. Should the approach followed by the Court be criticized? 
- Could it be said that, with regard to rules on the use of force, the existence of a general opinio juris supporting the existence of a rule prevails over specific acts of State practice which appear to be inconsistent with that rule? 

B) Consistency of practice and universality of rules. 
- What sort of consistency is required for a rule to be regarded as established? 
- In particular, how should one consider State conducts which are analogous but are based on different reasons? 
- How much practice is needed in order to recognize the existence of a rule? 
- How many States or groups of States should be involved? 
- Can the dearth of State practice be set off by consent or acquiescence of other States? 
- Is general international law on the use of force necessarily universal? 
- If universality is not a necessary precondition, how can the international community be segmented accordingly? 
- Can individual States be exempted from the respect due to principles and rules on the use of force? 

C) The relevance of passive conduct of States. 
- What is the weight to be given to the simple abstention from use of force, without any further qualification ? 
- What is the relevance of the lack of reaction towards measures implying the use of force by other States in order to establish the existence of a customary rule on the use of force? 
- Should this attitude of States necessarily be considered as evidence of an opinio juris in favour of the existence of a customary rule justifying the adoption of such measures? 
- If not, which circumstances are to be taken into account in order to determine the relevance of the passive conduct of States? 
- Whose conduct is to be considered as relevant: conduct of the directly injured State, of States having an interest, of the great powers, or of other States not having a qualified interest? 
- Can one rely only on the absence of protests against occasional violations of rules on the use of force in order to recognize the existence of a rule? 

D) Breach or development of international customary law. 
- Which elements are to be taken into account in order to establish whether a conduct inconsistent with a rule is to be treated as a breach of that rule or as an instance of practice creative of a new rule? 
- When can one say that the attitude of a State is directed towards creating a new rule? 
- What is the role of States which do not contribute to the material conduct? 


Session II 
Ascertaining International Customary Law on the Use of Force: 
The Role of Non-State Actors 

A) The Security Council. 
- When referring to international law on the use of force, the SC refers basically to the UN system: what is the relevance of these references for construing international customary law? 
- Is there a complete overlapping between the two systems or are there differences ? 
- Does the fact that the SC considers a certain conduct as giving rise to a threat to peace have an impact on general international law ? 
- What is the impact of the reference by the SC to a certain action as one allowing the right to self-defence (see, for instance, res. 1368(2001))? 
- Is there a difference between the two situations referred to above ? 
- When no SC resolution can be adopted because of the veto by one or more of its permanent members, to what extent does the existence of a widespread majority of States expressing a certain view have a bearing on the qualification of conduct under international customary law (Kosovo)? 
- To what extent can the failure by the SC to condemn a certain unilateral intervention and the subsequent recognition of the ensuing situation as a fait accompli be seen as an indication of the lawfulness of that intervention under international customary law (Kosovo and Iraq)? 
- What is the respective weight of SC findings and instances of State practice? 
- Do SC findings supplement State practice? 
- Do SC findings contribute to the formation of customary law only when they are followed by significant instances of State practice? 
- How effective must be the action by the SC in order to supplement the international body of customary rules ? 

B) General Assembly. 
- What is the impact on customary law of GA declarations or resolutions asserting in general terms the existence of a certain rule? 
- In particular, what has been the role of GA declarations in contributing to crystallize or generate customary rules on the use of force (see Nicaragua case)? 
- What is the impact on customary law of GA resolutions condemning or approving a specific armed intervention by a State? 
- What is the respective weight of the GA and of SC in contributing to shape the content of customary rules on the use of force? 
- In particular, when these two UN organs express different legal views, which elements ought to be taken into account in determining their respective weight ? 
- the different composition? 
- the distribution of competences under the UN Charter? 
- the different powers? 

C) International Court of Justice. 
- What is the methodology of construing international law on the use of force followed by the ICJ? 
- Since the ICJ does not, as a rule, analyze State practice, to which elements does it attach importance? 
- Reference to decisions of the ICJ are abundant in discussions on international customary law on the use of force (Corfu, Nicaragua, Nuclear Weapons). What is the role of these decisions? Are they, in particular, to be considered as elements of practice or rather as authoritative findings about the law? 
- Are there reasons to believe that with regard to the use of force the role of the ICJ in contributing to shape international customary law is less relevant than in other fields of international law (law of treaties, law of the sea)? 
- On the contrary, are there reasons to believe that ICJ's role is more significant in this area? 
- What has been so far the approach taken by the Court when called upon by States to ascertain the content of customary rules on the use of force? 
- In particular, can "judicial policy" of the Court in this context be characterised as activism or by self-restraint? 
- Has the ICJ's "judicial policy" changed in time? 

D) Regional Organizations. 
- To what extent does the practice of regional organizations contribute to the establishment of customary rules on the use of force? 
- Assuming that the conduct of regional organizations may be considered as practice relevant for establishing customary rules on the use of force, should one distinguish in this regard between acts adopted by an organization against a member State and acts adopted against a State which is not a member? 
- Is it conceivable that the conduct of a regional organization may create a particular customary rule on the use of force applicable in the relations between member States? 
- What is the impact of strategic concepts adopted by regional organisations on the evolution of customary law on the use of force ? 

E) Civil Society and NGOs 
- Is it conceivable that also civil society and NGO's have a role in developing customary rules on the use of force? 
- How can civil society and NGO's contribute to the formation of customary rules? 


Session III 
Use of Force and the Protection of Fundamental Values of the International Community 

A) Inductive approach v. value-oriented approach. 
- In construing rules of customary international law on the use of force, to what extent may one resort to a method that, instead of relying on an examination of State practice, is based on inferences from basic values shared by the international community? 
- From a methodological point of view, what are the main features of a method which consists in determining the content of the rules by inferences from the existence of basic values? 
- What is the relation between this method and the method which is based on empirical investigation of State practice? 
- In particular, should one consider that a value-oriented approach may merely supplement the inductive approach? 

B) Balancing the prohibition to use force with the need to protect human rights. 
- Given that the protection of human rights represents a core value of the international community, may it be said that the traditional test of State practice and opinio juris is not adequate when considering the issue of humanitarian intervention? 
- Is it more appropriate, with regard to this issue, to resort to a method which consists in balancing the two different values at stake, namely national sovereignty and protection of human rights? 
- What are the risks inherent in this way of reasoning? 
- Under what conditions may States rely on the need to protect human rights in order to justify the possibility to use force against another State? 
- In particular, may the plea of necessity be invoked in order to justify humanitarian intervention? 

C) Balancing the prohibition to use force and the need to combat terrorism. 
- May the need to combat terrorism be considered as an emerging value of the international community? 
- What is the impact, if any, of this emerging value on current rules on the use of force? 
- May the existence of new rules on the use of force be inferred from the process of balancing two different core values, namely national sovereignty and need to combat terrorism? 
- What could be the result of this balancing process? 
- In particular, could one envisage, in the light also of the recent practice (Afghanistan), that the rule on self-defence is undergoing a process of change? 

(This questionnaire has been prepared by Enzo Cannizzaro and Paolo Palchetti)