In the context of the 2005 attack that killed Prime Minister Rafic Hariri, the 2006 war with Israel, the 2008 internal armed conflict in Lebanon, the Syrian civil war and the current war in Gaza, this book studies the legal status of Hezbollah as a State or a non-State actor. There are important consequences to this distinction, ones that relate to international law, the qualification of an armed conflict and combatants as well as Lebanon's responsibilities toward the international community for complicity in the wrongdoings of a State (Iran) and a non-State actor (Hezbollah). After exploring Hezbollah's history and domestic law, the book argues that Lebanon legalised Hezbollah as an armed group and political party, and while Hezbollah acts at times as the State of Lebanon, it cannot be considered a State and subject of international law as it lacks State elements. As an alternative, Mireille Rebeiz proposes to adopt the theory of quasi-State, where a failed State co-exists with a non-State actor and shares its sovereignty. Following the 7th October attacks and the ongoing conflict with Israel, the question of the legal status of Hezbollah remains valid today.