For simplicity most banks require that a joint account be closed and a new one, with different ownership, be opened. But there is no federal law we know of that prevents the removal of one name from an account. We are not versed in the laws of each state. You might be able to call an attorney or state Attorney General and have your question answered.
Even if the policy of your bank requires the funds be transferred to a new account, there wouldn't be much you could do as that is the policy of the bank, and not any violation of law. (Again, unless state laws prohibit it. We don't think that is likely, but...)
When you have contacted an attorney, you might also ask what responsibility your spouse has as to support for you, and be aware too of how much you believe was in the account and the sources of those monies. You may need to know this.