Subsidiarity does not win cases: A mixed methods study of the relationship between margin of appreciation language and deference at the European Court of Human Rights

In August 2021, Protocol 15 inserted the doctrine of the margin of appreciation into the preamble of the European Convention of Human Rights, presumably cementing what President Spano has referred to as the 'Age of Subsidiarity', in which the European Court of Human Rights applies the margin of appreciation more often and increases deference to state parties. This insertion was done on the behest of the High Contracting Parties as part of the Interlaken reform process, and there is already a strong narrative in certain member states and parts of the scholarly literature that this focus has prompted the Court to increase the usage of the margin of appreciation and therefore the deference to states, judging more frequently in their favour. This article hypothesizes, however, that the increased usage of the margin of appreciation language which has been taken as proof for this narrative, might not, in fact, indicate higher levels of deference. Rather, the language of the margin of appreciation could be the result of usage by other actors or a marker of complexity for so-called 'hard cases'. To investigate this relationship, the article applies a mixed legal-doctrinal and quantitative methodology to analyse who in the case law invokes the doctrine, what their purpose is for doing so, and what adjudicative consequences follow. It finds that usage of the margin-language topped well before the Interlaken process began, that governments are not the most frequent invokers and that, statistically speaking, states are no more likely to win margin-cases than other cases.