7

From the start, the Constitution concerned the sources of private law essentially because it defined the competences of laws and regulations. Since the beginning of the 1970s, it has gradually changed in nature and has become, through various procedural as well as substantial mechanisms, the source of private law. The Constitution has thus acquired a horizontal dimension. The constitutional argument has entered the courtrooms. However, this fundamental mutation has not occurred without difficulties. For private law, the Constitution remains a foreign body, which reception and acclimatization are still uncertain.