When application wants to create new Aggregate based on an already existing Aggregate, we are allowed to copy everything ( except for the inner entities's IDs ) inside the existing Aggregate into a new Aggregate. But if some inner object references an object outside the Aggregate boundary, we're not allowed to also copy the referenced object.
a) I know Aggregates should mind their own business and not interfere with other Aggregate's life cycle, but what exactly would be wrong if we also copied the object existing outside the Aggregate boundary?