summary There are two important Belgian laws referring to psychiatric disturbances that may prove dangerous. The Civil Code includes the law relating to the protection of the mentally ill person, dated 26th June 1990, better known as the law of civil commitment of the mentally ill. Since April, 2007, the Penal Code has contained a new law on the internment of people with a psychiatric disorder; this new law replaces the old law of the 1st July, 1964, meant to protect the society. Although the two laws apply to different fields, in clinical practice there are sometimes 'grey areas' where it is not immediately evident which legal framework is applicable. Starting from a case study in which the civil judge ordered the civil commitment of a detainee, we explore these 'grey areas' and compare the two legal frameworks. We base our study on the new law on internment, clarify it and sketch the legal history of internment in Belgium.