Index: components/portal/src/java/org/apache/jetspeed/decoration/DecorationValve.java
===================================================================
--- components/portal/src/java/org/apache/jetspeed/decoration/DecorationValve.java	(revision 408599)
+++ components/portal/src/java/org/apache/jetspeed/decoration/DecorationValve.java	(working copy)
@@ -87,6 +87,16 @@
             decorationFactory.clearCache(requestContext);
         }
         ContentPage page = requestContext.getPage();
+
+        // Globaly override all psml themes if override session attribute has been set
+        if (requestContext
+                .getSessionAttribute(PortalReservedParameters.PAGE_THEME_OVERRIDE_ATTRIBUTE) != null)
+        {
+            String decoratorName = (String) requestContext
+                    .getSessionAttribute(PortalReservedParameters.PAGE_THEME_OVERRIDE_ATTRIBUTE);
+            page.setDefaultDecorator(decoratorName, Fragment.LAYOUT);
+        }
+
         Theme theme = decorationFactory.getTheme(page, requestContext);
 
         requestContext.setAttribute(PortalReservedParameters.PAGE_THEME_ATTRIBUTE, theme);
Index: components/portal/src/java/org/apache/jetspeed/login/LoginProxyServlet.java
===================================================================
--- components/portal/src/java/org/apache/jetspeed/login/LoginProxyServlet.java	(revision 408599)
+++ components/portal/src/java/org/apache/jetspeed/login/LoginProxyServlet.java	(working copy)
@@ -23,6 +23,8 @@
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.HttpSession;
 
+import org.apache.jetspeed.PortalReservedParameters;
+
 /**
  * LoginProxyServlet
  * 
@@ -55,6 +57,17 @@
         else
             session.removeAttribute(LoginConstants.PASSWORD);
 
+        // Globaly override all psml themes
+        if (request
+                .getParameter(PortalReservedParameters.PAGE_THEME_OVERRIDE_ATTRIBUTE) != null)
+        {
+            String decoratorName = request
+                    .getParameter(PortalReservedParameters.PAGE_THEME_OVERRIDE_ATTRIBUTE);
+            session.setAttribute(
+                    PortalReservedParameters.PAGE_THEME_OVERRIDE_ATTRIBUTE,
+                    decoratorName);
+        }
+
         response.sendRedirect(response.encodeURL(request.getContextPath()
                 + "/login/redirector"));
     }
Index: jetspeed-api/src/java/org/apache/jetspeed/PortalReservedParameters.java
===================================================================
--- jetspeed-api/src/java/org/apache/jetspeed/PortalReservedParameters.java	(revision 408599)
+++ jetspeed-api/src/java/org/apache/jetspeed/PortalReservedParameters.java	(working copy)
@@ -53,6 +53,11 @@
     public static final String RESOVLER_CACHE_ATTR = "org.apache.jetspeed.resovler.cache";
     public static final String PORTLET_WINDOW_ATTRIBUTE = "org.apache.jetspeed.portlet.window";
     public static final String PAGE_THEME_ATTRIBUTE = "org.apache.jetspeed.theme";
+    /**
+     * Setting this as a session attribute will override all themes declared in
+     * psml. Sample values are "simple", "tigris", "jetspeed"
+     */
+    public static final String PAGE_THEME_OVERRIDE_ATTRIBUTE = "org.apache.jetspeed.theme.override";
     public static final String PORTAL_FILTER_ATTRIBUTE = "org.apache.jetspeed.login.filter.PortalFilter";
     
 }