Thomas Liefländer is a doctoral candidate at St Hugh’s College, University of Oxford
Any attempt to come to terms with the notion of proportionality, be it in the context of the use of force in self-defence or anywhere else, has to grapple with a number of questions. First, what is the nature of the applicable proportionality test? Possible answers include ‘tit-for-tat’, ‘not-more-than-necessary’ or the ‘narrow proportionality test’ which assesses whether the ‘good’ effects of a measure outweigh its ‘bad’ effects. Secondly, once this question is settled, a more precise definition of the various factors going into the proportionality equation and how they interrelate is needed. Finally, how is each factor to be assessed under the conditions of epistemic and normative uncertainty that exist in the real world? Depending on the context, the answer to any one of these questions can be straightforward or very difficult. In self-defence, it seems, they are mostly difficult.
Professor Kretzmer’s recent EJIL article tackles some of these questions. He focuses, in particular, on the definition of the legitimate ends of self-defence and how they impact on the proportionality test. In summary, he first suggests that the definition of legitimate goals can determine whether a ‘tit-for-tat’ or ‘not-more-than-necessary’ test is applicable. Secondly, identifying the legitimate aims is crucial for being able to apply both the ‘not-more-than-necessary’ and the ‘narrow proportionality’ test, as both relate action taken in self-defence to the good (ie the legitimate ends) it intends to achieve. In these two respects, Professor Kretzmer’s contribution is outstanding. His work will certainly focus the discussion on the centrality that the definition of legitimate ends has both for self-defence in general and the issue of proportionality in particular. However, in stressing this particular aspect Professor Kretzmer may have downplayed the role of the remaining questions to some degree. I shall outline the important questions that Professor Kretzmer’s article essentially leaves open. In doing so, I will briefly touch on (1) the status of the ‘narrow proportionality’ test, (2) the ‘means’ side of the ‘means-end/not-more-than-necessary’ test, and finally (3) on the more general issue of proportionality-assessments under epistemic and normative uncertainty. My intention is not so much to challenge Professor Kretzmer’s arguments, but rather to extend – but not complete – the picture of what it is that we argue about when proportionality is in issue.