This isn't possible using navigation rules in JSF 1.x. Use ExternalContext#redirect()
instead.
public void action() throws IOException {
// ...
ExternalContext ec = FacesContext.getCurrentInstance().getExternalContext();
String url = ec.getRequestContextPath() + "/page.jsf?someparam=" + URLEncoder.encode(someparam, "UTF-8");
ec.redirect(url);
}