How would I restrict certain user levels from editing categories

by

You would need to remove the capability for a Editor role to manage_categories

add_action( 'init', 'remove_editor_manage_categories' ); 

function remove_editor_manage_categories() {

$role = get_role( 'editor' );
$role->remove_cap( 'manage_categories' );
}

Source http://codex.wordpress.org/Function_Reference/remove_cap