Limiting Posting To Specific Categories

I want to limit the ability of a blogger to post to certain categories, and I want to be able to control the display of posts in certain other categories.

For example, I may want to disallow the ability of the blogger to post to a category named "Featured." Rather, I would have a separate plugin which allows the upload of data from a form into that post.

Another example, I may want to disallow the ability of the blogger to post to a category named "News." Rather, I would want the ability to display specific pre-written posts as the blogger raises their level in ProSites. Display "Post A" at Level 2, "Post A" and "Post B" at Level 3, etc. These are posts which display adverts for products the blogger has purchased the rights to sell.

How can I perform these two actions?