How to limit taxonomy term selection

This might help:

http://wordpress.stackexchange.com/questions/3633/how-to-filter-post-post-content-prior-to-save

A crude solution (or maybe the only solution) would be to filter out the unwanted taxonomies just before the post is saved to the database.

You may also write a jQuery routine to prevent the user from adding too many taxonomies in the first place. That would be the elegant way, but you’d still have to use a WordPress filter in case the user circumvents your jQuery method.