sergio said:Should he go to the US embassy? Are there any free legal services for immigrants facing deportation? Can any knowledgeable member offer to speak with him about this?
Call the embassy, but embassy's these days generally aren't in the business of saving their citizen's asses when they have knowingly broken the laws of the country they are staying in (especially when those laws are in essence equivalent to US law). Maybe they'll lend an ear for a few minutes, but unless it's a case that's really going to make the news, unfortunately there may not be a lot of help there other than a pat on his back and a "Get yourself back to your own country, son".
Upon entering a country, be it as a tourist or on another visa status, it is understood that you are subjecting yourself to that country's laws and all that they may mean for you. Embassies tend to help in situations where it may cause their country embarassment, where there is a big difference in their law vs. that of another countries (ie this brouhaha over child custody happening in Japan), where both countries are signatories to a law and one is not upholding it (ie the child custody case going on in Brazil) or where a VIP is involved.
It's worth a call, after all he is a citizen, they will talk to him, but I don't think they'll be able to do anything to stop the deportation if the whole process has been lawful (questionable of course, but in Argentina that could take years to fight).