Index: wp-includes/nav-menu.php
===================================================================
--- wp-includes/nav-menu.php	(revision 15288)
+++ wp-includes/nav-menu.php	(working copy)
@@ -78,7 +78,22 @@
 	$_wp_registered_nav_menus = array_merge( (array) $_wp_registered_nav_menus, $locations );
 }
 
+
 /**
+ * Unregisters a navigation menu for a theme.
+ *
+ * @param array $location the menu location identifier
+ */
+function unregister_nav_menu( $location ) {
+	global $_wp_registered_nav_menus;
+
+	if (array_key_exists( $location, $_wp_registered_nav_menus ) )
+		unset( $_wp_registered_nav_menus[$location] );
+}
+
+
+
+/**
  * Register a navigation menu for a theme.
  *
  * @since 3.0.0