Target node in the active hierarchy is an end node with articles

What causes this issue?

The target node in the active hierarchy is an end node that has article
assignments. If you copy, a node that is not an end node in an active
hierarchy would have article assignments. This is not permitted.

System Response

Copying is not permitted.

How to fix this error?

From the source hierarchy, copy the same branch with the source nodes
above it, or delete/reassign the article assignments from the target
node in the active hierarchy.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.