Minn. R. Civ. P. 19.01
A person who is subject to service of process shall be joined as a party in the action if (a) in the person's absence complete relief cannot be accorded among those already parties, or (b) the person claims an interest relating to the subject of the action and is so situated that the disposition of the action in the person's absence may (1) as a practical matter impair or impede the person's ability to protect that interest or (2) leave any one already a party subject to a substantial risk or incurring double, multiple, or otherwise inconsistent obligations by reason of the person's claimed interest. If the person has not been so joined, the court shall order that the person be made a party. If the person should join as a plaintiff but refuses to do so, the person may be made a defendant, or, in a proper case, an involuntary plaintiff.
Minn. R. Civ. P. 19.01