Case assignment rules are rules that automatically assign cases to users or queues based on certain criteria.
You can create a case assignment rule to ensure that cases are owned by a user when they are closed, by setting the criteria to match the closed case status and the action to assign the case to the user who last modified it. This way, you can prevent cases from being closed while still owned by a queue. To correct the existing problem of hundreds of cases that are closed but still owned by a queue, you can use a data tool such as Data Loader or Import Wizard to update the owner field on those cases in bulk. Verified References: [Case Assignment Rules] and [Data Tools]