Consolidation of lawsuits may be ordered by a court when two or more lawsuits involving the same or similar parties (plaintiff and defendant), legal issues, and factual issues are pending in the same court or in different courts in the same jurisdiction (state court system or federal court system). If the lawsuits are pending in different courts one case may be transferred to the other court, and the cases consolidated there.

Laws and rules regarding the consolidation—or transfer and consolidation—of lawsuits vary from state to state and in the federal court system.

In New York, consolidation of lawsuits is governed by the New York Civil Practice Law and Rules (CPLR). According to CPLR Article 6 (Sections 602 and 603), a court has the discretion to order consolidation or a joint trial of actions involving common questions of law or fact to avoid unnecessary costs or delay. This can occur when two or more lawsuits are pending in the same court or when actions are pending in different courts within the state. If the actions are in different courts, one may be transferred to the other for consolidation purposes. The decision to consolidate is based on the court's determination that the consolidation would serve the interests of justice and efficiency. In the federal court system, Rule 42 of the Federal Rules of Civil Procedure allows for similar consolidation when actions involve a common question of law or fact. The decision to consolidate federal cases is at the discretion of the federal court. It's important to note that while consolidation can streamline litigation, it must also protect the rights and interests of all parties involved.