The purpose of this article is to explore the possibility of using the social theory of the French philosopher and historian Michel Foucault to the study of the legal discourse. Foucault’s theory is part of a broadly defined critical theory of law, whose task is to show the unconscious or political determinants of the legal discourse. In particular, Foucault shows the moments in which the legal discourse collides with other discourses — psychiatric and disciplinary. The power struggle appearing in those moments, that is the situation when one of the discourses is trying to seize power over another, allows to newly formulate the problem of autonomy of the legal discourse and its emancipatory possibilities. An example of such a struggle is what happened with Pierre Rivière — which is the moment in which the legal discourse has lost some of its power in favor of the psychiatric discourse. A recent case of Mariusz T. in Poland indicates the topicality of this issue, which shows the emergence of a new form of mental power, ie. the therapeutic power.