如何使用环回来保护不同角色的属性

I was just wondering how you would restrict property access to the $owner role only. For instance in my case I have a Joke which has an Author. The Author has User as base. I would like other "Authers" / Users to see who created the Joke, but they should not be able to see the Authers email, only if the Author is the $owner of the Joke itself it should be OK to show their email, just for the sake of this case. I was just wondering how you would restrict pro