Under international law, sending a military force into another sovereign state without that state’s permission is classified as an illegal invasion. A UN peacekeeping force cannot enter a member state’s territory unless that state has given prior consent. Furthermore, Britain could have vetoed a UN decision as a member of the Security Council. Even if the UN ruled Britain as a party to the dispute, neutralising its veto, the Cold War alliance between Britain and the US would most likely have seen the US veto decisions on Britain’s behalf. The Irish government astutely recognised that Irish military intervention could only be internationally justified in the event of a total breakdown of law and order in Northern Ireland. Under these circumstances Irish intervention could not be labelled as an assault on British sovereignty. On the contrary, the Irish government could have successfully claimed that it authorised cross-border operations primarily for humanitarian reasons in response to Britain’s failures under humanitarian law.