Interesting discussion.
On the matter of an Italian citizen willing to desenbark at FCO (i it was menat?) or otherwise enter the country, I can assure you that he/she has that right at any time and circumstance, as long you have a valid ID (passport mainly).
Immigration police can say whatever, fill the guy with a lecture about regolamention that exist only in their minds, but because natural law, once he is firm on ground in italy he has the right to enter it, only subjet to custom obligations of course. There isn't even any fine they can possibly impose, the right for a national citizen to go back on is natural law.
I think this is the same for any country of the world.