The continued US military presence in the country, against the wishes of the Iraqi government and parliament, is a breach of international law. […]
Beyond this, there are very few truly accepted justifications which a country can rely on to legitimately use force within another’s territory. One exception is a doctrine called “intervention by invitation”, where one country is given express permission to take military action in another country by that country’s government. Alongside other rules that govern this kind of interaction, there are also rules on when a state overstays its welcome and becomes in breach of its international obligations.
For example, the Definition of Aggression, a text adopted by the UN which outlines what is considered aggression under international law, sets out that if the state intervening breaks the conditions, or extends its presence on the territory, this counts as an act of aggression. This was put forward as a claim in a case between the Democratic Republic of Congo (DRC) and Uganda in 2005. The DRC claimed that Uganda’s ongoing use of force on its territory, after it had stopped giving consent, amounted to aggression. Although in this particular case the International Court of Justice did not find Uganda’s actions were an act of aggression, the court did rule that Uganda had breached the UN Charter’s basic prohibition of force. As a result it was clearly established that a country cannot maintain a military presence within another country after it has been asked to leave. Läs artikel