Why does the system allow a return of a purchase order with an associated invoice?

Summary:

Why does the system allow a return of a purchase order with an associated invoice?

Content (please ensure you mask any confidential information):

It has been identified that the system allows returns to be made on purchase orders that have an associated invoice; if the 3-way is handled, the system should not allow returns to be made while there is an invoice associated with the PO.

Version (include the version you are using, if applicable):

24B

Code Snippet (add any code snippets that support your topic, if applicable):