In November 1979 the US government froze over $14 billion of Iranian assets in response to the Iranian revolution and the seizure of US hostages. Since then, freezing sovereign assets has become an increasingly frequent and highly effective economic sanction. It has been used against Nicaragua, Libya, Panama, Kuwait and Iraq. This book is a comprehensive study of asset-freezing as an economic sanction and a political weapon. It analyses the international financial, legal and political implications of asset-freezing. It concentrates on the freeze against Iran to discover the initial motivations and mechanisms of asset-freezing. The book examines its political, economic and legal basis: beginning with the US International Emergency Economic Powers Act of 1977; through the legal implications of the extraterritorial application of the freeze order and the litigation in European courts; and ending with an examination of the political agreement that resolved the Iranian crisis in 1981. It shows how this agreement superseded litigation in the US courts which would have produced judgments far more favourable to Iran. Finally, there is a comparative analysis of freezes after the Iranian case and suggestions for the ways in which countries vulnerable to asset-freezing can protect themselves against this unilateral instrument of hegemony by a major financial power.