diff -ru orig/wp-includes/taxonomy.php new/wp-includes/taxonomy.php
--- orig/wp-includes/taxonomy.php	2010-07-30 23:35:41.647845088 +0100
+++ new/wp-includes/taxonomy.php	2010-07-30 23:36:53.115880419 +0100
@@ -397,6 +397,37 @@
 	return true;
 }
 
+/**
+ * Remvoe an already registered taxonomy from an object type.
+ *
+ * @package WordPress
+ * @subpackage Taxonomy
+ * @since 3.0.2
+ * @uses $wp_taxonomies Modifies taxonomy object
+ *
+ * @param string $taxonomy Name of taxonomy object
+ * @param string $object_type Name of the object type
+ * @return bool True if successful, false if not
+ */
+function unregister_taxonomy_from_object_type($taxonomy, $object_type) {
+
+	global $wp_taxonomies;
+
+	if ( !isset($wp_taxonomies[$taxonomy]) )
+		return false;
+
+	if ( ! get_post_type_object($object_type) )
+		return false;
+
+	foreach (array_keys($wp_taxonomies['category']->object_type) as $array_key) {
+		if ($wp_taxonomies['category']->object_type[$array_key] == $object_type) {
+			unset ($wp_taxonomies['category']->object_type[$array_key]);
+			return true;
+		}
+	}
+	return false;
+
+}
 //
 // Term API
 //