Limiting Categories

I'm moving my church's site from a self hosted WP to Squarespace.  My goal is that the simpler and less tech intensive interface will make it easier to get more people involved in maintaining the site and adding content.

One thing I need to do is have a predefined set of categories for blog posts. I don't want anyone to be adding new categories.  Tags are more fluid and I'm fine with adding new tags as we go, but I want our category list to be small and well defined.

It looks like categories and tags are treated exactly the same, they can be added at will when posts are created.  I definitely want to limit that, how can I do so?  Is there a way to do that? I looked through permissions, hoping there was a level that locked category changes, but didn't see anything in there about categories.

Content contributors have access to all content but can't change site settings. Cats are set in the blog page itself. If someone is going to actually post and publish a blog post or content, they will have access to the categories and tags. You can only ask them to not change or add any, which if they tried to do will find it isn't that easy.