Legitimacy cannot be applied to nation-states since they arise as a consequence of violent confrontation or civil uprising. That goes for the UK, US, France, Germany and Israel. Once a people have gained power, or those claiming to represent that people, over a particular territory then the task is to gain the recognition of others - not legitimacy. In the present day, the UN appears to have taken on that role. So, if the notion of legitimacy does not apply neither can the notion of de-legitimization.