You cannot petition an in-law. I am therefore going to assume you are talking about the Affidavit of Support. If so, there is no way to revoke it. See link below.
Additionally, if they had a baby together, then she obviously did not marry your son just for the green card. I just do not understand why people assume that because a marriage fails it was just for the green card.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.
You don't have it within your power to revoke anything. If you signed a joint affidavit and she got the green card based on this, you are obligated. See link for when the obligation runs out.
If you have actual evidence of fraud, you can supply it to USCIS or ICE and see if they'll do anything - but just her leaving isn't proof of fraud.
She would at first have likely gotten a conditional green card good for just two years - would have then needed to "remove conditions" to get a ten year card or the status expired. Not clear if this was done here.
Is she has a green card, it is unlikely you can withdraw your I-864 affidavit of support
Neil I Fleischer (513) 977-4209 www.immigrate2usa.com Note: Neil Fleischer is an attorney licensed in the State of Ohio The below answer is provided for informational use only. One should not act or refrain to act solely based on the information provided. No attorney/client relationship is created unless an Agreement is signed by the attorney and the client. Best regards, Neil Neil I Fleischer The Fleischer Law Firm, LLC 917 Main Street Cincinnati, Ohio 45202-1314 Direct telephone: 513 977 4209 email@example.com Enjoy our Blog at http://immigrate2usa.blogspot.com/
You cannot revoke her green card. You are still under obligation under the Affidavit of support but only if she collects a government benefit. Assuming your son is supporting his child and divorce/separation issues have been resolved, that is not likely to occur. The focus should be on the domestic relations issue, not immigration.
Under the guidelines set by AVVO, this response is general information only and not specific legal advice, and no attorney client relationship is formed by this response to your question.