This article analyses, from an eminently legal perspective, the particularly vulnerable situation of migrants in an irregular situation. This irregular status notably increases migrants’ risk of suffering human rights violations, underscoring the high level of impunity enjoyed by states that commit such violations. Faced with this state of affairs, and by means of a comparative analysis of the case law emanating from European and inter-American regional legal systems, this study explores the possibility of irregular or undocumented migrants being included in the classification of “vulnerable group”. The meaning of this expression is being shaped in international courts of justice, and in particular the European Court of Human Rights and Inter-American Court of Human Rights. The study concludes that establishing this interpretation would facilitate access to those judicial bodies, offering an instrument to protect irregular migrants against the discriminatory practices engaged in by transit and host countries. Equally, it opens up the possibility of international migrants in an irregular situation benefitting from the “positive discrimination” measures handed down in some states and designed specifically to tackle such groups.