I reside outside of the U.S. right now, however, my ex-husband (though he is still working on his divorce papers) got the check through our old joint bank account and refuses to send it to me.
He explains that since I am not physically in the U.S. he can not send my check to me and he would get in legal trouble if he sent it.
I have a social security number, I filed my taxes in 2018, and my Green Card is not expired yet.
Can I trust him that he will send it back to the government or should I get a lawyer to get the check back?
You say you "ex-husband" is working on his divorce papers. Does that mean he is working on the divorce papers from you? The divorce papers that he or you filed in California? If the California divorce is not finished between you and him, then he is not your ex-husband yet. It sounds like he received a double-$1,200 check, $2,400 total. I am sure he is not sending it back because then he would be sending his half back also. So he is probably depositing all of it. That means you need to ask the judge in the divorce to order him to give you your 41,200. To do that you need to file a Request For Order, form FL-300. If you cannot afford an attorney, you can go to the Self-Help Center at the courthouse where your divorce papers are filed. You can also telephone the Self-Help Center and ask if they can help you with your papers over the phone. Some of the Self-Help Centers are giving help over the phone. So it may not matter that you are outside the U.S. Don't sign any agreement with your husband unless it has a sentence that he will send you the $1,200.