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 Virginia, the rules for intervention in a lawsuit are governed by state statutes and court rules. A person or entity, not originally a party to a lawsuit, may intervene by filing a plea in intervention before the court renders a judgment. The process does not require the court's permission, but the intervention can be challenged by an existing party through a motion to strike. The right to intervene is established if the potential intervenor has a significant legal interest in the case, such that they could have initiated the same lawsuit or defended against it. The court may only strike an intervention if it fails to meet the criteria of having a justiciable interest, if it excessively complicates the issues, or if the intervention is not crucial for protecting the intervenor's interests. If an intervention is struck despite meeting these conditions, it may be considered an abuse of discretion by the trial court. It is important for intervenors to demonstrate that their involvement is necessary to protect their legal interests without unduly complicating the proceedings.