[from the other article posted here] "Mr Frattini said, and presented figures showing that out of the 650,000 illegal immigrants who were ordered to leave last year, two-thirds of them avoided expulsion and stayed in the union."
The EU charter doesn't prevent it. The problem is with Malta's proximity to Africa and the failure to do anything about it. Same goes for Europe. If Turkey is brought into the EU, the problem will get even worse, because sneak-ins from Iraq/Jordan/Iran/Syria/West Bank/Gaza etc will be able to leave Turkey for other EU countries with little trouble (even less than now).
Things like 'can't deport to a country that may use torture', 'can't deport to a country that refuses to accept them back', 'may not deport to a country that may impose the death penalty', 'may only deport to country of origin; not to a third country', and many other restrictions, as well as technical errors made in their cases, etc.
BTW back in the late 1960's my mother lived in Valletta for two years, while my father worked in the Libyan oilfields, pre-Ghadaffi. That was when my parents sold & moved out on me, since I had intention of moving out of the house.