Can we block issue creation capabilities for a client "contributor"?

[Laura Meine]

We have a need for some of our client contacts to be able to contribute to existing tickets (view and add comments).  However, they should not be able to log new requests.

I created a project role that has not been assigned to the Create Issue permission and I've assigned that to a user, but it still allows them to create a new issue from the portal.

[Brant Schroeder]

@Laura Meine 

If the customer has access to the portal to contribute on an issue they will be able to raise a request as well.  The project role you are looking at relates to the creation of issue in Jira and not the portal.  There currently is not functionality to prevent users from creating issues if they can access the portal.