You can sponsor him for a green card. He may need an I-601 waiver in order to qualify.
(213) 394-4554 x0 Mr. Shusterman is a former INS Trial Attorney (1976-82) with over 35 years of immigration experience. His response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.
You didn't tell us how long you have been in Argentina ... nor did you tell us if you left voluntarily ... two very important facts.
Mr. Shusterman is correct, he may need a waiver.
Meet with a US licensed attorney ... many of us do these consultations by Skype.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.
The first step would be to file an I-130 visa petition. He will need a waiver in order to be granted a visa if he was unlawfully present in the US for more than 180 days after he turned 18. The application process will take at least 8 months.
Possibly with an i601 waiver but more facts are needed.
You may take a look at some educational materials on I-601 waivers here: www.swagatusa.com/educational-materials.
Be sure to talk to an attorney.
Dhenu Savla, Esq.
This answer does not create an attorney-client relationship and is not meant to be relied upon as legal advice.