Symposium on Erin Pobjie’s Prohibited Force: Toward a Higher Level of Analytical Clarity – An Introductory Reflection on Erin Pobjie’s ‘Prohibited Force’

[Claus Kreß is a Professor of Criminal Law and Public International Law, the Chair for German and International Criminal Law, and Director of the Institute of International Peace and Security Law at the University of Cologne. He formerly Served in the German Federal Ministry of Justice.]

In para. 253 of its 19 July 2024 Advisory Opinion in Legal Consequences from the Policies and Practices of Israel in Occupied Palestinian Territory, Including East Jerusalem, the International Court of Justice (ICJ) observes ‘that an occupation involves, by its very nature, a continued use of force in foreign territory’. But contrary to the impression that the Court conveys through its apodictic formulation, the legal accuracy of this statement is by no means self-evident. Rather, as Erin Pobjie shows on pages 162 to 164 of her book, the Court’s interpretation of the concept of ‘use of force’ is not free from controversy. Pobjie refers to Judge Kooijmans’ Separate Opinion in the ICJ’s Armed Activities case. One can now add to this Judge Charlesworth’s Declaration, as appended to the Advisory Opinion in Legal Consequences, in order to indicate that a measure of uncertainty continues to exist within the ICJ even to date. For in para. 15 of her Declaration, Judge Charlesworth nuances the above cited formulation in paragraph 253 of the Advisory Opinion by saying that ‘an occupation involves, by its very nature, a continued threat or use of force in foreign territory (emphasis added by me)’. On page 164 of her book, Pobjie herself expresses her inclination toward the ICJ’s position. But rather than deriving this position from the ‘very nature’ of military occupation, Pobjie’s central argument consists of referring to the subsequent agreement among States about the interpretation in question, as embodied in Article 3(a) of the annex to United Nations’ General Assembly Resolution 3314 (XXIX) of 14 December 1974. In view of the fact, that military occupation, by its ‘very nature’, does not imply the use of weapons, Pobjie characterizes military occupation as an ‘anomalous’ example of the use of force. All this is just one reason why it is difficult to disagree with the starting point of Pobjie’s analysis that   

‘Despite the central importance of this provision in the international legal order, there remains genuine uncertainty among States, scholars and jurists about the meaning of a prohibited ‘use of force’ under article 2(4) of the UN Charter and customary international law.’

In the same vein, one can point to the present uncertainty about the right answers to be given to questions such as whether the use of force within the meaning of the prohibition must pass a certain gravity threshold, what level of directness between the means employed and the (potential physical) effects is required, whether there is a need to distinguish the use of force within the meaning of the prohibition from forcible police measures or whether the term ‘use of force’ implies an element of intentionality.

That this state of affairs leaves much to desire is another basic assumption of Pobjie’s work (see pages 4 to 11) which I find hard not to concur with. For not only constitutes the prohibition of the use of force, in the well-chosen words of the ICJ in paragraph 148 in the Armed Activities case a ‘cornerstone of the United Nations Charter’, but because the existence of a use of force also entails distinct legal consequences. Regrettably, the ICJ has not spelled out this point in sufficient clarity in paragraph 261 of its Advisory Opinion Legal Consequence, but both the Joint Declaration of Judges Nolte and Cleveland and the Declaration of Judge Charlesworth helpfully provide for clarity in that respect. Hence, one cannot but agree with the author’s conviction (articulated on page 231 of her book) that ‘for such a foundational rule of the international legal system, it is not satisfactory to apply vague, ad hoc standards’ to determine whether or not potentially forcible incidents fall within the scope of the prohibition of the use of force.

Having had the great pleasure of being Erin Pobjie’s supervisor during her work on the PhD-thesis out of which ‘Prohibited Force’ has grown, I do not find it appropriate here to engage in a scholarly discussion of one or the other of the author’s arguments and findings. Instead, I hope that may be allowed to take this opportunity to repeat here what I have stated in my foreword to the book: In my humble view, the central contribution of this elegantly written study consists of the suggestion to treat the term ‘use of force’ as a type rather than a concept and to identify a basket of elements which, while not having all to be present must be weighed and balanced to determine whether the threshold for the definition is met. It is by no means a weakness, but it rather testifies to the author’s unfailing scholarly spirit that she does not pretend to be able to apply her innovative approach to all conceivable questions of delineation in a work that she has thankfully kept to an accessible size. Instead, the author has carefully chosen a number of illustrative case studies in order to demonstrate by way of examples the work her new methodology is capable of doing. Apart from making for enjoyable and stimulating reading, these practical applications put the author’s approach to the reader’s test in all due concreteness and transparency. Pobjie does not make the bold assertion that the use of her methodology will yield incontrovertible results in all possible instances. More modestly, but probably more realistically, she claims that it provides a shared language and coherent framework for legal analysis and scholarly debate regarding the content of a prohibited ‘use of force’ between States under international law. In that vein, her carefully worded conclusion on page 232 reads as follows:  

‘The framework of type theory has the potential to facilitate clearer analysis of “uses of force” between States. It is hoped that this clarity will in turn lead to greater compliance with the prohibition of the use of force between States in their international relations and contribute to our shared endeavour of international peace and security.”

As I indicated above, ‘military occupation’ constitutes another example where Pobjie’s analytical framework allows for analysis and explanation of the law, which, perhaps understandably, the ICJ has refrained from providing in his Advisory Opinion in Legal Consequences.

The book’s potential ‘to facilitate clearer analysis’ allows for a significant advance in strengthening the international legal order in one of its core components. For this reason alone, Erin Pobjie’s book deserves the closest attention of international lawyers worldwide. Opinio Juris is thus much to be commended to convene this symposium and I greatly look forward to reading the engagements with her book which shall form part of this scholarly conversation.