I can answer that as he was a good friend of mine, and i spoke to Bajo Cero who tried his best to help us today.
Basically my friend, and fellow forum member, went to Canada for a few weeks and returned as per normal through EZE. bad luck would have him questioned, detained, and ultimately in the next two hours put back on his flight to Toronto. no entry possible.
bad luck all round.
1) as Bajo Cero says, today was the last day of court holidays and Bajo was not able to reach anyone.
2) even if he was to get a judge and try to keep my friend in the country (as he was trying to get citizenship), the plane back to Toronto was 2 hours after he landed. same plane. no time for any real interventions.
3) the immigrations reviewed his passport and saw he had been living here over a few years, with multiple in and outs, some before the 3 month period, some after (fines paid each time). they took him into a detention room. they took his phone. they would not allow him to talk to a lawyer and then marched him to the plane. they asked that he paid his own flight back, but in the end, let him on "for free". it is unsure if air Canada will charge him at a later date.
he was not a criminal, not gainfully employed, enjoying life here on savings but overstaying the legal 3 months time frame.
i don't want to debate if it was right or wrong, only that this is real. it happened and who knows now how and if he can come back.
be careful, things are a changing...