If a joint sponsor for immigration fails to fulfill their obligations, they may be subject to consequences. These could include not proceeding with the application process or paying back the benefits they have already provided.
If the joint sponsor cannot provide adequate financial support, you as the applicant may be forced to take legal action against them to obtain the necessary funds. In such cases, it becomes possible for you to file a lawsuit and seek damages from them for not fulfilling their obligation of sponsoring you as a part of the immigration process. If your sponsor fails to update your address with the USCIS, this could lead to them being fined $250 to $5,000 based on whether it was intentional.
Green card holders have rarely taken this action against sponsors. Regarding what actions can be taken against a non-compliant joint sponsor, there are a few options available depending on the specifics of each situation.
The government could press charges to demand repayment of public benefits received, as well as for collection costs and legal fees associated with bringing the case to court. In most cases, these proceedings are rare, but sponsors need to understand that the failure to meet their financial commitments creates a potential liability.