Rarely the situation arises where an individual finds out that their spouse is still married to someone else. What is done in this case?
If someone was previously married and never obtained a divorce, intentionally or not, the subsequent marriage is considered by the court to never have taken place. Legally, it is prohibited and considered void and grounds for an annulment. There is nothing that can be done by either party to fix it, other than for the married spouse to obtain a divorce and the parties to legally marry again.
In some cases where there is no property, no children, and no debts shared between the spouses, this situation may not pose much of a problem. The parties are able to go their separate ways and there are no legal ties connecting the two of them. One party may have to go through the name change procedure, but it should pretty much take care of any connection they have.
Sometimes, if there are children involved or the parties have acquired property or debt, it can be more problematic. Under Minnesota law, marital property is anything acquired (assets or debts) from the time parties are married until some point in the divorce proceedings. If one spouse has been supporting the other and has accumulated savings, retirement benefits, or other assets, and that spouse is legally still married to another person, the subsequent spouse is out of luck. They have no legal claim to any of the property, and would have no claim for spousal maintenance following the separation.