A person or entity who is not a party to a lawsuit generally may intervene in the lawsuit and become a party to it by filing a plea in intervention prior to the entry of the court’s judgment—provided the court does not reject (strike) the intervention. An intervenor is not required to secure the court’s permission to intervene, and the party who opposed the intervention has the burden to challenge it by filing a motion to strike.

A person or entity has a right to intervene if the intervenor could have brought the same lawsuit, or any part of it in his own name—or, if the action had been brought against him, he would be able to defeat the lawsuit, or some part of it.

A trial court abuses its discretion by striking an intervention if (1) the intervenor meets the above test, (2) the intervention will not complicate the case by an excessive multiplication of the issues, and (3) the intervention is almost essential to effectively protect the intervenor’s interest.

In Michigan, the rules for intervention in a lawsuit are governed by the Michigan Court Rules (MCR). Specifically, MCR 2.209 outlines the conditions under which a non-party may intervene in a lawsuit. A person or entity may intervene in a lawsuit if they have an interest that is or may be affected by the outcome of the litigation. The intervenor must file a timely application before the court's judgment. The court does not need to grant permission for the intervention, but the party opposing the intervention can challenge it by filing a motion to strike. The right to intervene is established if the intervenor could have initiated the same lawsuit or if they could defend against it if the action were brought against them. A trial court may be found to have abused its discretion if it strikes an intervention that meets the criteria of having a significant interest in the case, not overly complicating the case, and being nearly essential for protecting the intervenor's interests. It is important to note that while Michigan law provides a framework for intervention, the specifics of each case can affect the application of these rules, and an attorney can provide guidance on the likelihood of successful intervention.