Allow edit but disable delete?

Is there an easy way to allow a user to edit a node, but not delete it? I know that might sound wierd, but I have a site where there are a few defined sets of several pages that are created by a main admin, and then the editing duties are passed off to another admin who is just in charge of day to day updates for a particular set. I could just make sure the update admins are trained not to delete the nodes, but I would like to just remove that possiblity altogether.

I was looking at taxonomy_access, and it looks like it should do most what I need, but the delete permission isn't working like I would expect. What I'm doing:

1. assigning all content pages in the set to a specific taxonomy term.

2. assigning the user to a updater role for that set.

3. in category permissions, I check the "view" and "update" permissions for that set, but leave "Delete" unchecked.

I do this for a few different users with a few different sets of content, and the users only see the content they are supposed to, but they can also delete content, which they're not supposed to be able to.

I know in general a user should be able to delete a node they have access to edit, but this is a special case. Anyone have any ideas? I searched the forums for a good long while but couldn't come up with anything.

Thanks!
Robby