Article 25.2 of the Spanish Constitution of 1978 prescribes the guidance of the imprisonment penalties towards the rehabilitation and social reintegration, conferring therefore constitutional relevance to the foundations and limits of the exercise of “ius puniendi” (right to punish) by the State. First of all this essay aims to offer a general approach to the issues concerning the rehabilitation and reintegration order of the imprisonment penalties in the context of the limiting action of the State power during the complete punishment process. As well as analyze the meaning of the exit furloughs established by the penitentiary legislation to satisfy the constitutional mandate of reintegration of the punished.