Abstract
A comparative study is made of two cases tried before the European Court of Human Rights: M. v. Germany and Del Río Prada v. Spain; in both cases, the constitutional courts of those countries acted as a power of the State and not as defenders of the Constitution, by preventing the release of individuals considered dangerous or socially undesirable. This prolonged deprivation of liberty was carried out in violation of basic principles of the criminal and constitutional system, and is the result of a regressive criminal policy; therefore, the European Court of Human Rights declares the violation of the principles of criminal legality and liberty, protected in the European Convention on Human Rights, for which it not only resorts to a material interpretation of the rights and principles undermined, but rejects the formal arguments that conceal their violation.