This situation would be very "fact-intensive," meaning it would depend on the facts of the case. The most obvious problem is that the husband could be charged with illegally possessing the firearm because he is a convicted felon. He could also be charged with violating his probation. The wife's criminal exposure could depend on many factors, such as her intent in buying it (she could be described as a "straw-buyer), and whether she is purposefully aiding her husband in violating the law against a convicted felon possessing a firearm. She should consult a lawyer so the lawyer can assess her legal exposure.