Lawyers for Tehran, which brought its case to the ICJ in 2016, told judges that Washington had breached a 1955 friendship treaty by allowing American courts to confiscate some $2 billion in Iranian assets, including $1.75 billion from the Central Bank of Iran.
This was done to pay damages to victims of what the US claimed were terrorist attacks sponsored by Iran. Iran denies supporting terrorism, Reuters reported.
At the ICJ court, Iran's representative Tavakol Habibzadeh said that the US ruling opened the way for "billions of dollars in compensation and punitive damages through default judgements".
"By doing so the United States have created an industry of litigation against Iran and Iranian companies," said Habibzadeh, who heads Iran's Centre for Legal Affairs, AFP wrote.
Another lawyer for Iran, Vaughan Lowe, said Iran "denies that it is responsible for the injuries to those victims."
"United States legislation doesn't bother with proof or with attribution, or with responsibility," he said. ""Never mind proving that Iran is guilty in any particular case… Sentence first, verdict afterwards."
Iran argues the US seizure of Iranian financial assets and those of Iranian companies is illegal, adding that resolving the case is crucial at a time when Iran is facing economic difficulties after sanctions.
The 1950s friendship treaty was signed long before Iran's 1979 Islamic Revolution, which toppled the US-backed shah, and the subsequent severing of US-Iranian relations.
After Iran filed two complaints based on the 1955 treaty – which accords the ICJ jurisdiction – Washington formally withdrew from the accord in 2018.
In turn Washington has unsuccessfully tried to get the lawsuit thrown out, alleging that Iran's "unclean hands" should disqualify its bid to recover the $2 billion of assets.
The ICJ, also known as the World Court, is the United Nations' top court. It was set up after World War II to resolve disputes between member states. Its rulings are binding and cannot be appealed, but it has no means of enforcing them.