N.B. As per the disclaimer, neither the ICRC nor the authors can be identified with the opinions expressed in the Cases and Documents. Some cases even come to solutions that clearly violate IHL. They are nevertheless worthy of discussion, if only to raise a challenge to display more humanity in armed conflicts. Similarly, in some of the texts used in the case studies, the facts may not always be proven; nevertheless, they have been selected because they highlight interesting IHL issues and are thus published for didactic purposes.

[Source: ICJ, Nicaragua v. United States of America, Military and Paramilitary Activities, Judgement of 27 June 1986, Merits; online: http://www.icj-cij.org]




Judgment - para. 80 to 207


  1. [...] The Court finds it established that, on a date in late 1983 or early 1984, the President of the United States authorized a United States government agency to lay mines in Nicaraguan ports; that in early 1984 mines were laid in or close to the ports of El Bluff, Corinto and Puerto Sandino, either in Nicaraguan internal waters or in its territorial sea or both, by persons in the pay and acting on the instructions of that agency, under the supervision and with the logistic support of United States agents; that neither before the laying of the mines, nor subsequently, did the United States Government issue any public and official warning to international shipping of the existence and location of the mines; and that personal and material injury was caused by the explosion of the mines [...].


  1. The Court finds at all events that from 1981 until September 30, 1984 the United States Government was providing funds for military and paramilitary activities by the contras [the armed opposition to the government of Nicaragua] in Nicaragua, and thereafter for “humanitarian assistance”. [...]


  1. [...]The United States participation, even if preponderant or decisive, in the financing, organizing, training, supplying and equipping of the contras, the selection of its military or paramilitary targets, and the planning of the whole of its operation, is still insufficient in itself, on the basis of the evidence in the possession of the Court, for the purpose of attributing to the United States the acts committed by the contras in the course of their military or paramilitary operations in Nicaragua. All the forms of United States participation mentioned above, and even the general control by the respondent State over a force with a high degree of dependency on it, would not in themselves mean, without further evidence, that the United States directed or enforced the perpetration of the acts contrary to human rights and humanitarian law alleged by the applicant State. Such acts could well be committed by members of the contras without the control of the United States. For this conduct to give rise to legal responsibility of the United States, it would in principle have to be proved that State had effective control of the military or paramilitary operations in the course of which the alleged violations were committed.
  2. The Court does not consider that the assistance given by the United States to the contras warrants the conclusion that these forces are subject to the United States to such an extent that any acts they have committed are imputable to that State. It takes the view that the contras remain responsible for their acts, and that the United States is not responsible for the acts of the contras, but for its own conduct vis-à-vis Nicaragua, including conduct related to the acts of the contras. What the court has to investigate is not the complaints relating to alleged violations of humanitarian law by the contras, regarded by Nicaragua as imputable to the United States, but rather unlawful acts for which the United States may be responsible directly in connection with the activities of the contras. The lawfulness or otherwise of such acts of the United States is a question different from the violations of humanitarian law of which the contras may or may not have been guilty. It is for this reason that the Court does not have to determine whether the violations of humanitarian law attributed to the contras were in fact committed by them. At the same time, the question whether the United States Government was, or must have been, aware at the relevant time that allegations of breaches of humanitarian law were being made against the contras is relevant to an assessment of the lawfulness of the action of the United States. In this respect, the material facts are primarily those connected with the issue in 1983 of a manual of psychological operations.
  3. Nicaragua has in fact produced in evidence before the Court two publications which it claims were prepared by the CIA and supplied to the contras in 1983. The first of these, in Spanish, is entitled “Operaciones sicológicas en guerra de guerrillas” (Psychological Operations in Guerrilla Warfare), by “Tayacan”, the certified copy supplied to the Court carries no publisher’s name or date. In its Preface, the publication is described as

“a manual for training of guerrillas in psychological operations, and its application to the concrete case of the Christian and democratic crusade being waged in Nicaragua by the Freedom Commandos”. [...]

  1. The Court concludes that in 1983 an agency of the United States Government supplied to the FDN a manual on psychological guerrilla warfare which, while expressly discouraging indiscriminate violence against civilians, considered the possible necessity of shooting civilians who were attempting to leave a town; and advised the “neutralization” for propaganda purposes of local judges, officials or notables after the semblance of trial in the presence of the population. The text supplied to the contras also advised the use of professional criminals to perform unspecified “jobs”, and the use of provocation at mass demonstrations to produce violence on the part of the authorities so as to make “martyrs”. [...]

[Because of a reservation made by the US in accepting the jurisdiction of the ICJ, the Court could not apply multilateral treaties to the facts of the case.]

  1. [...] The Court would observe that, according to the United States argument, it should refrain from applying the rules of customary international law because they have been “subsumed” and “supervened” by those of international treaty law, and especially those of the United Nations Charter. Thus the United States apparently takes the view that the existence of principles in the United Nations Charter precludes the possibility that similar rules might exist independently in customary international law, either because existing customary rules had been incorporated into the Charter, or because the Charter influenced the later adoption of customary rules with a corresponding content.
  2. The Court does not consider that, in the areas of law relevant to the present dispute, it can be claimed that all the customary rules which may be invoked have a content exactly identical to that of the rules contained in the treaties which cannot be applied by virtue of the United States reservation. On a number of points, the areas governed by the two sources of law do not exactly overlap, and the substantive rules in which they are framed are not identical in content. But in addition, even if a treaty norm and a customary norm relevant to the present dispute were to have exactly the same content, this would not be a reason for the Court to take the view that the operation of the treaty process must necessarily deprive the customary norm of its separate applicability. Nor can the multilateral treaty reservation be interpreted as meaning that, once applicable to a given dispute, it would exclude the application of any rule of customary international law the content of which was the same as, or analogous to, that of the treaty law rule which had caused the reservation to become effective.
  3. [...] The Court therefore finds that Article 51 of the Charter is only meaningful on the basis that there is a “natural” or “inherent” right of self-defence, and it is hard to see how this can be other than of a customary nature, even if its present content has been confirmed and influenced by the Charter. Moreover the Charter, having itself recognized the existence of this right, does not go on to regulate directly all aspects of its content. For example, it does not contain any specific rule whereby self-defence would warrant only measures which are proportional to the armed attack and necessary to respond to it, a rule well established in customary international law. [...]
  4. [...] The existence of identical rules in international treaty law and customary law has been clearly recognized by the Court in the North Sea Continental Shelf cases. To a large extent, those cases turned on the question whether a rule enshrined in a treaty also existed as a customary rule, either because the treaty had merely codified the custom, or caused it to “crystallize”, or because it had influenced its subsequent adoption. The Court [...] considered it to be clear that certain other articles of the treaty in question “were ... regarded as reflecting, or as crystallizing, received or at least emergent rules of customary international law” (I.C.J. Reports 1969, p. 39, para. 63). [...]
  5. There are a number of reasons for considering that, even if two norms belonging to two sources of international law appear identical in content, and even if the States in question are bound by these rules both on the level of treaty-law and on that of customary international law, these norms retain a separate existence. This is so from the standpoint of their applicability. In a legal dispute affecting two States, one of them may argue that the applicability of a treaty rule to its own conduct depends on the other State’s conduct in respect of the application of other rules, on other subjects, also included in the same treaty. [...] Rules which are identical in treaty law and in customary international law are also distinguishable by reference to the methods of interpretation and application. A State may accept a rule contained in a treaty not simply because it favours the application of the rule itself, but also because the treaty establishes what that State regards as desirable institutions or mechanisms to ensure implementation of the rule. Thus, if that rule parallels a rule of customary international law, two rules of the same content are subject to separate treatment as regards the organs competent to verify their implementation, depending on whether they are customary rules or treaty rules. The present dispute illustrates this point. [...]
  6. [...] Far from having constituted a marked departure from a customary international law which still exists unmodified, the Charter gave expression in this field to principles already present in customary international law, and that law has in the subsequent four decades developed under the influence of the Charter, to such an extent that a number of rules contained in the Charter have acquired a status independent of it. [...]
  7. The Court concludes that it should exercise the jurisdiction conferred upon it by the United States declaration of acceptance under Article 36, paragraph 2, of the Statute, to determine the claims of Nicaragua based upon customary international law [...].
  8. In the present dispute, the Court, while exercising its jurisdiction only in respect of the application of the customary rules of non-use of force and non-intervention, cannot disregard the fact that the Parties are bound by these rules as a matter of treaty law and of customary international law. Furthermore, in the present case, apart from the treaty commitments binding the Parties to the rules in question, there are various instances of their having expressed recognition of the validity thereof as customary international law in other ways. It is therefore in the light of this “subjective element” – the expression used by the Court in its 1969 Judgement in the North Sea Continental Shelf cases (I.C.J. Reports 1969, p. 44) – that the Court has to appraise the relevant practice.
  9. It is not to be expected that in the practice of States the application of the rules in question should have been perfect, in the sense that States should have refrained, with complete consistency, from the use of force or from intervention in each other’s internal affairs. The Court does not consider that, for a rule to be established as customary, the corresponding practice must be in absolutely rigorous conformity with the rule. In order to deduce the existence of customary rules, the Court deems it sufficient that the conduct of States should, in general, be consistent with such rules, and that instances of States conduct inconsistent with a given rule should generally have been treated as breaches of that rule, not as indications of the recognition of a new rule. If a State acts in a way prima facie incompatible with a recognized rule, but defends its conduct by appealing to exceptions or justifications contained within the rule itself, then whether or not the State’s conduct is in fact justifiable on that basis, the significance of that attitude is to confirm rather than to weaken the rule. [...]
  10. [...] The significance for the Court of cases of State conduct prima facie inconsistent with the principle of non-intervention lies in the nature of the ground offered as justification. Reliance by a State on a novel right or an unprecedented exception to the principle might, if shared in principle by other States, tend towards a modification of customary international law. In fact however the Court finds that States have not justified their conduct by reference to a new right of intervention or a new exception to the principle of its prohibition. [...]


Judgment - para. 215 to 292

  1. The Court has noted above (paragraph 77 in fine) that the United States did not issue any warning or notification of the presence of the mines which had been laid in or near the ports of Nicaragua. Yet even in time of war, the Convention relative to the laying of automatic submarine contact mines of October 18, 1907 (the Hague Convention No. VIII) provides that “every possible precaution must be taken for the security of peaceful shipping” and belligerents are bound “to notify the danger zones as soon as military exigencies permit, by a notice addressed to ship owners, which must also be communicated to the Governments through the diplomatic channel” (Art. 3). Neutral Powers which lay mines off their own coasts must issue a similar notification, in advance (Art. 4). It has already been made clear above that in peacetime for one State to lay mines in the internal or territorial water of another is an unlawful act; but in addition, if a State lays mines in any waters whatever in which the vessels of another State have rights of access or passage, and fails to give any warning or notification whatsoever, in disregard of the security of peaceful shipping, it commits a breach of the principles of humanitarian law underlying the specific provisions of Convention No. VIII of 1907. Those principles were expressed by the Court in the Corfu Channel case as follows “certain general and well recognized principles, namely: elementary considerations of humanity, even more exacting in peace than in war” (I.C.J. Reports 1949, p. 22).
  1. This last consideration leads the Court on to examination of the international humanitarian law applicable to the dispute. Clearly, use of force may in some circumstances raise questions of such law. [...]
  2.  [...] The conduct of the United States may be judged according to the fundamental general principles of humanitarian law; in its view, the Geneva Conventions are in some respects a development, and in other respects no more than the expression, of such principles. It is significant in this respect that, according to the terms of the Conventions, the denunciation of one of them “shall in no way impair the obligations which the Parties to the conflict shall remain bound to fulfil by virtue of the principles of the law of nations, as they result from the usage established among civilized peoples, from the laws of humanity and the dictates of the public conscience” (Convention I, Art. 63; Convention II, Art. 62; Convention III, Art. 142; Convention IV, Art. 158). Article 3 which is common to all four Geneva Conventions of August 12, 1949 defines certain rules to be applied in the armed conflicts of a non-international character. There is no doubt that, in the event of international armed conflicts, these rules also constitute a minimum yardstick, in addition to the more elaborate rules which are also to apply to international conflicts; and they are rules which, in the Court’s opinion, reflect what the Court in 1949 called “elementary considerations of humanity” (Corfu Channel, Merits, I.C.J. Reports 1949, p. 22; paragraph 215 above). The Court may therefore find them applicable to the present dispute, and is thus not required to decide what role the United States multilateral treaty reservation might otherwise play in regard to the treaties in question. [In his separate opinion, I.C.J. Reports 1986, p. 183, Roberto Ago writes on this point: “6. [...] I am bound to express serious reservations with regard to the seeming facility with which the Court – while expressly denying that all the customary rules are identical in content to the rule in the treaties (para. 175) – has nevertheless concluded in respect of certain key matters that there is a virtual identity of content as between customary international law and the law enshrined in certain major multilateral treaties concluded on a universal or regional plane. [...] I am moreover most reluctant to be persuaded that any broad identity of content exists between the Geneva Conventions and certain ‘fundamental general principles of humanitarian law’, which, according to the Court, were pre-existent in customary law, to which the Conventions ‘merely give expression’ (para. 220) or of which they are at most ‘in some respects a development’ (para. 218). Fortunately, after pointing out that the Applicant has not relied on the four Geneva Conventions of 12 August 1949, the Court has shown caution in regard to the consequences of applying this idea, which in itself is debatable.”]  
  1. The conflict between the contras’ forces and those of the Government of Nicaragua is an armed conflict which is “not of an international character”. The acts of the contras towards the Nicaraguan Government are therefore governed by the law applicable to conflicts of that character; whereas the actions of the United States in and against Nicaragua fall under the legal rules relating to international conflicts. Because the minimum rules applicable to international and to non-international conflicts are identical, there is no need to address the question whether those actions must be looked at in the context of the rules which operate for the one or for the other category of conflict. The relevant principles are to be looked for in the provisions of Article 3 of each of the four Conventions of August 12, 1949, the text of which, identical in each Convention, expressly refers to conflict not having an international character.
  2. The Court considers that there is an obligation on the United States Government, in the terms of Article 1 of the Geneva Conventions, to “respect” the Conventions and even “to ensure respect” for them “in all circumstances”, since such an obligation does not derive only from the Conventions themselves, but from the general principles of humanitarian law to which the Conventions merely give specific expression. The United States is thus under an obligation not to encourage persons or groups engaged in the conflict in Nicaragua to act in violation of the provisions of Article 3 common to the four 1949 Geneva Conventions, which reads as follows: [Here the full text of this Article is quoted] [...]
  1. The Court therefore finds that the support given by the United States, up to the end of September 1984, to the military and paramilitary activities of the contras in Nicaragua, by financial support, training, supply of weapons, intelligence and logistic support, constitutes a clear breach of the principle of non-intervention. The Court has however taken note that, with effect from the beginning of the United States governmental financial year 1985, namely 1 October 1984, the United States Congress has restricted the use of the funds appropriated for assistance to the contras to “humanitarian assistance” [...]. There can be no doubt that the provision of strictly humanitarian aid to persons or forces in another country, whatever their political affiliations or objectives, cannot be regarded as unlawful intervention, or as in any other way contrary to international law. The characteristics of such aid were indicated in the first and second of the fundamental principles declared by the Twentieth International Conference of the Red Cross, that “The Red Cross, born of desire to bring assistance without discrimination to the wounded on the battlefield, endeavours – in its international and national capacity – to prevent and alleviate human suffering wherever it may be found. Its purpose is to protect life and health and to ensure respect for the human being. It promotes mutual understanding, friendship, co-operation and lasting peace amongst all peoples” and that “It makes no discrimination as to nationality, race, religious beliefs, class or political opinions. It endeavours only to relieve suffering, giving priority to the most urgent cases of distress.”
  1. The United States legislation which limited aid to the contras to humanitarian assistance however also defined what was meant by such assistance, namely: “the provision of food, clothing, medicine, and other humanitarian assistance, and it does not include the provision of weapons, weapons systems, ammunition, or other equipment, vehicles, or material which can be used to inflict serious bodily harm or death” [...]. It is also to be noted that, while the United States Congress has directed that the CIA and Department of Defense are not to administer any of the funds voted, it was understood that intelligence information might be “shared” with the contras. Since the Court has no information as to the interpretation in fact given to the Congress decision, or as to whether intelligence information is in fact still being supplied to the contras, it will limit itself to a declaration as to how the law applies in this respect. An essential feature of truly humanitarian aid is that it is given “without discrimination” of any kind. In view of the Court, if the provision of “humanitarian assistance” is to escape condemnation as an intervention in the internal affairs of Nicaragua, not only must it be limited to the purposes hallowed in the practice of the Red Cross, namely “to prevent and alleviate human suffering”, and “to protect life and health and to ensure respect for the human being”; it must also, and above all, be given without discrimination to all in need in Nicaragua, not merely to the contras and their dependants.


  1. Having concluded that the activities of the United States in relation to the activities of the contras in Nicaragua constitute prima facie acts of intervention, the Court must next consider whether they may nevertheless be justified on some legal ground. As the Court has stated, the principle of non-intervention derives from customary international law. It would certainly lose its effectiveness as a principle of law if intervention were to be justified by a mere request for assistance made by an opposition group in another State - supposing such a request to have actually been made by an opposition to the regime in Nicaragua in this instance. Indeed, it is difficult to see what would remain of the principle of non-intervention in international law if intervention, which is already allowable at the request of the government of a State, were also to be allowed at the request of the opposition. This would permit any State to intervene at any moment in the internal affairs of another State, whether at the request of the government or at the request of its opposition. Such a situation does not in the Court's view correspond to the present state of international law.


  1. The Court now turns to the question of the application of humanitarian law to the activities of the United States complained of in this case. Mention has already been made (paragraph 215 above) of the violations of customary international law by reason of the failure to give notice of the mining of the Nicaraguan ports, for which the Court has found the United States directly responsible. Except as regards the mines, Nicaragua has not however attributed any breach of humanitarian law to either United States personnel or the “UCLAs” [”Unilaterally Controlled Latino Assets” acronym used by the CIA for Latin American citizens, paid by, and acting under the direct instructions of, United States military or intelligence personnel], as distinct from the contras. The Applicant has claimed that acts perpetrated by the contras constitute breaches of the “fundamental norms protecting human rights”; it has not raised the question of the law applicable in the event of conflict such as that between the contras and the established Government. In effect, Nicaragua is accusing the contras of violations both of the law of human rights and humanitarian law, and is attributing responsibility for these acts to the United States. The Court has however found (paragraphs 115, 216) that this submission of Nicaragua cannot be upheld; but it has also found the United States responsible for the publication and dissemination of the manual on “Psychological Operations in Guerrilla Warfare” referred to in paragraphs 118 to 122 above.
  2. The Court has also found (paragraphs 219 and 220 above) that general principles of humanitarian law include a particular prohibition, accepted by States, and extending to activities which occur in the context of armed conflicts, whether international in character or not. By virtue of such general principles, the United States is bound to refrain from encouragement of persons or groups engaged in the conflict in Nicaragua to commit violations of Article 3 which is common to all four Geneva Conventions of August 12, 1949. The question here does not of course relate to the definition of the circumstances in which one State may be regarded as responsible for acts carried out by another State, which probably do not include the possibility of incitement. The Court takes note of the advice given in the manual on psychological operations to “neutralize” certain “carefully selected and planned targets”, including judges, police officers, State Security officials, etc., after the local population have been gathered in order to “take part in the act and formulate accusations against the oppressor”. In view of the Court, this must be regarded as contrary to the prohibition in Article 3 of the Geneva Conventions, with respect to non-combatants, of “the passing of sentences and the carrying out of executions without previous judgement pronounced by a regularly constituted court, affording all the judicial guarantees which are recognized as indispensable by civilized peoples” and probably also of the prohibition of “violence to life and person, in particular murder to all kinds, ... .”
  1. It is also appropriate to recall the circumstances in which the manual of psychological operations was issued. When considering whether the publication of such a manual, encouraging the commission of acts contrary to general principles of humanitarian law, is unlawful, it is material to consider whether that encouragement was offered to persons in circumstances where the commission of such acts was likely or foreseeable. The Court has however found [...] that at the relevant time those responsible for the issue of the manual were aware of, at the least, allegations that the behaviour of the contras in the field was not consistent with humanitarian law; it was in fact even claimed by the CIA that the purpose of the manual was to “moderate” such behaviour. The publication and dissemination of a manual in fact containing the advice quoted above must therefore be regarded as an encouragement, which was likely to be effective, to commit acts contrary to general principles of international humanitarian law reflected in treaties. [...]

Having concluded that the activities of the United States in relation to the activities of the contras in Nicaragua constitute prima facie acts of intervention, the Court must next consider whether they may nevertheless be justified on some legal ground. As the Court has stated, the principle of non-intervention derives from customary international law. It would certainly lose its effectiveness as a principle of law if intervention were to be justified by a mere request for assistance made by an opposition group in another State - supposing such a request to have actually been made by an opposition to the regime in Nicaragua in this instance. Indeed, it is difficult to see what would remain of the principle of non-intervention in international law if intervention, which is already allowable at the request of the government of a State, were also to be allowed at the request of the opposition. This would permit any State to intervene at any moment in the internal affairs of another State, whether at the request of the government or at the request of its opposition. Such a situation does not in the Court's view correspond to the present state of international law.




(8)    By fourteen votes to one,

Decides that the United States of America, by failing to make known the existence and location of the mines laid by it, referred to in subparagraph (6) hereof, has acted in breach of its obligations under customary international law in this respect; [...]

(9)    By fourteen votes to one,

Finds that the United States of America, by producing in 1983 a manual entitled Operaciones sicológicas en guerra de guerillas, and disseminating it to contra forces, has encouraged the commission by them of acts contrary to general principles of humanitarian law: but does not find a basis for concluding that any such acts which may have been committed are imputable to the United States of America as acts of the United States of America; [...]


  1. (Paras 174-178, 181) Does a rule of customary international law continue to be in force between States party to a multilateral treaty codifying that rule? Even if the two rules are identical? Why? May the contents of the customary rule be influenced by the treaty rule? By the practice of States bound by the treaty?
  2. (Paras 185, 186, 207) Does a treaty commitment “count” as practice for customary international law? Can a rule belong to customary international law even if the behaviour of States frequently fails to conform with the rule in question? What is the importance of the Court’s ruling on these points for IHL?
  3. (Para. 219) How does the Court qualify the conflict in Nicaragua?
  4. (Paras 80, 215, 254) Was the laying of mines in or near the ports of Nicaragua a violation of international law? Of IHL? What did violate IHL? Was IHL at all applicable? (Hague Convention VIII, Arts 3-4)
  5. (Paras 218, 219) Does Art. 3 common to the Conventions apply to international armed conflicts? As customary law? Does the Martens Clause prove that Art. 3 common to the Conventions is customary law? That the whole of IHL is customary law?
  6. (Para. 220) Is Art. 1 common to the Conventions applicable in non-international armed conflicts? As a treaty rule? As a customary rule? Or both?
  7. (Paras 115-122, 254-256, 292(9))
    1. Is the US responsible for all acts of the contras? For their violations of IHL? For some of the IHL violations? Why? Under which conditions would the US be responsible for all acts of the contras? Would that modify the Court’s qualification of the conflict?
    2. Is the US violating IHL by providing the Manual “Operaciones sicológicas en guerra de guerrillas”? Regardless of whether the contras actually committed the recommended acts? Which rules of IHL are violated?
  8. (Paras 242, 243)
    1. Can providing humanitarian assistance violate international law? Are the rules violated those of IHL or those of jus ad bellum?
    2. Are the conditions for lawful humanitarian assistance prescribed by IHL? (GC IV, Arts 23 and 59; P I, Art. 70; P II, Art. 18; CIHL, Rules 55-56) Are the fundamental principles of the Red Cross part of IHL? To whom are they addressed? Must States comply with the fundamental principles of the Red Cross?
    3. Which aspect of the US humanitarian assistance to the contras violated international law? (P I, Art. 70; P II, Art. 18)
    4. Does a State providing strictly humanitarian assistance to only one side in an international armed conflict violate international law? Does the other side have an obligation to let such assistance through? (P IArt. 70; GC IV, Arts 23 and 59)