In occasion of the 70th anniversary of the American Declaration of the Rights and Duties of Man, this article concentrates on the analysis of the principle of equality before the law. Hence, the first of the two sections which compose this work examines the legal value of the cited instrument. To this end, a joint interpretation of the organs (Inter-American Court and Commission of Human Rights) that comprise the Inter-American System of Human Rights and the scholar positions in this respect will be carried out. The second section addresses the definition of the principle of equality before the law within the aforementioned regional system. It thus starts off from a theoretical analysis and progressively addresses its specific and contemporary content through the interpretation of the existing case-law and the advisory opinions issued in this context.