I married someone who was here in the United States illegally. With my help, he obtained his US residency and green card. We are now separated after eight years of marriage, and are in the process of getting a divorce. He has been calling me, texting and e-mailing me constantly because he wants me to give him my US citizenship information so that he may become a US citizen. I have informed him numerous times that I will not be giving him the information because I found out through some friends that he brought a woman from Argentina (where he is from) to the United States and her four children and is planning to marry her. The problem is that he will not stop harassing me. My question is am I obligated by law to give him my citizenship information since we are still married? If I am not obligated by law, can I accuse him of harassment? He will not stop contacting me to the point that he has threatened me. Any help or suggestions would be greatly appreciated.
Thank you.

Ok, I'm not a lawyer but harassment or any kind is illegal. You are in a good position because you hold the key to his citizenship... contact an immigration office and they will advise you best.
good luck =]

Stop all contact, document all harassment, and ask your divorce lawyer about what exactly if anything you have to reveal (through the lawyer).