Schengen helps divide Europe as not all members take part.  The Schengen Area, adopted by some countries in Europe but not others, will create a difference of interest which will irrevocably divide the EU over time. The fact that not all the EU members are part of the Schengen agreement means that the EU is divided in two areas: one in which the free movement of people is achieved and one in which it is not. This threatens to create two different ways of approaching the questions of justice and security within the EU: one that is managed through the SIS system and Europol, and one that is managed through the traditional justice and home affairs legislation within the Union framework itself. This could turn out to be a particularly divisive force within a Union that is already faltering having failed to sign a common Constitution and settled for a watered down treaty instead.