How to avoid delete to item that already assigned organizations ?

Summary:

We want to prevent an item that is assigned to organizations from being deleted. How can I do this? If using an Item Rule, how should the rule be written?

Content (please ensure you mask any confidential information): I did something but did not worked. You can see attachment.

Version (include the version you are using, if applicable):25B

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