Restrict categories to specific users?

How could categories be restricted for use by specific users during post creation? I’m looking into using a second instance of WordPress as a job board. I want to use categories for organizations, but I also want only specific users to be able to post for certain organizations.

Ideally, categories available to specific users would be displayed in the the Categories sidebar only to those specific users. I imagine this would involve use of the Role Manager plugin.

The short-term solution would, of course, be post moderation…