Penitentiary law is made up of the set of legal rules that regulate the execution of sentences and measures of deprivation of liberty imposed for the commission of a crime. These rules are mainly found in the General Penitentiary Organic Law and have, as a provincial objective, the reeducation and social reintegration of persons who have been sentenced to custodial sentences, as well as their custody and retention.

Persons who are sentenced to a custodial sentence and who must therefore enter a penitentiary center are classified into different degrees of treatment, depending on their personality, their social and family history, their criminal record, the length of the sentence or measure imposed… The degrees of treatment are as follows:

1. First degree, which corresponds to the closed regime.
2. Second degree, which corresponds to the ordinary regime.
3. Third degree, which corresponds to the open regime.
4. Fourth degree, which corresponds to parole.

The classification of a person in a certain grade is important because it determines, on the one hand, the type of penitentiary establishment in which he must remain and, on the other hand, the applicable penitentiary regime and the release permits and other penitentiary benefits to which he may be entitled.

Throughout the term of imprisonment, the convicted person may advance in grade, thus passing through the different prison regimes, and may also regress (i.e. return to a lower grade). In each of the regimes, and especially from the third degree classification onwards, convicted persons are eligible for certain prison leave or other prison benefits, which allow them to return progressively to life in freedom.