Question: How do I limit a user from being able to see a Model or Library in a Mart that they have at least Viewer Rights for in erwin Mart r9?
Solution: There is not a way to prevent the users from seeing and opening any model in the Mart as read-only, you can only prevent them from having write access on all the models. This is done by giving them only the viewer right at the Mart level and then make them a modeler profile on the libraries where they are supposed to have write access.
The only way to prevent a User from having access at all Models or Libraries would be to create a second Mart Server that would be a secure Mart. You can then move all the confidential models to this Mart and give just the few users who need to have access logins on the second Mart.