Two names on title, can one party make a voluntary repossession?

On the vehicle title held by the bank, both my name and my ex-partners names are on the title. There is no 'and' or 'or' on the title between our names so the assumption is that it's an 'and'. He is the primary on the vehicle loan. We in the process of separating (not from a marriage) for good this time and child custody and support issues. This vehicle was acquired and he made the vehicle payments each month with the child support money he should've been giving me and this we agreed to (verbally). Payments on this vehicle are not behind or delinquent. Can he just go ahead a do a voluntary repossession without my knowledge or consent? Is there anything I can do? I'm not in a financial position to take over the entire loan on my own.