The script only works for EN and probably legal-content so don't try to apply it to other pages.
@@ -1,7 +1,7 @@
// ==UserScript==
// @name eur-lex toc
// @namespace eur-lex
-// @include http://eur-lex.europa.eu/*
+// @include http://eur-lex.europa.eu/legal-content/EN/*
// @version 1
// @grant none
// ==/UserScript==