The Court confirmed that nationals of Member States have the right to enter the territory of other Member States in the exercise of the various freedoms recognized by the Treaty and in particular the freedom to provide services, which is enjoyed by both the providers and the recipients of services.
The Court held that the establishment of conditions of entry other than the production of a valid passport or identity card was inconsistent with Union law. (full text)

The Court decided that Member States have the right to check the nationality of EU citizens entering their territory by an internal Union frontier, until harmonisation measures concerning the crossing of external frontiers are adopted.
The presentation of a valid identity card or passport is the only way to distinguish nationals of non-EU States from nationals of Member States of the Union. (full text)