The EU Return Directive demands that immigrant detention be as short as possible, but, by logical implication, this also means that detention can be as long as necessary. What concerns the maximum length of detention, the Return Directive is remarkably generous: Immigrants can be detained for a period of up to eighteen months—a deprivation of liberty that is otherwise justified only as punishment for serious crimes. The practice of such long-term detention, now burgeoning, is highly questionable for moral, practical, and—our focus—legal reasons.

The European Convention of Human Rights (ECHR) provides the relevant yardstick. While discussions on the legality of immigrant detention have focused on requirements of necessity, we shift attention towards the surprisingly absent question of maximum duration. Our analysis delves into the drafting context of the ECHR to reveal that it only authorizes the pre-removal detention of immigrants for markedly short periods. Picking up the interpretative canon of the regime, we note that meanings can of course change, but we argue that it is a legal mistake to consider that long-term detention is now sanctioned by the Convention.