A New York judge is considering whether to allow a lawsuit brought by victims of South Africa's apartheid-era regime.
Mr Fagan is seeking big money for apartheid victims
They are seeking damages from multi-nationals, including banks, oil companies and manufacturers.
It is alleged that they supported the apartheid regime in South Africa contravening United Nations sanctions.
The South African Government fears the case could scare off foreign investors. Holocaust victims secured $1.2bn in a settlement with Swiss banks in 1998.
The judge, John Sprizzo, has not yet decided whether he will allow the case to go forward, but during the hearing he questioned the argument that doing business with South Africa under apartheid had in itself been a violation of international law.
The BBC's New York Correspondent, Jane Standley, says this case is being seen as crucial for four lawsuits which have now begun against a growing number of multi-national companies and banks.
This New York case was the first one filed - in June last year - under an obscure statute dating back to 1789.
The Alien Torts Claims Act allows legal action for human rights abuses to be taken against companies which do business in the United States.
The claim alleges that computer companies benefited from selling software to the South African police and that oil companies made money from breaking the international trade embargo.
It is being brought by Ed Fagan - a controversial American lawyer - who successfully brought a class action suit in 1998 against banks in Switzerland for holding on to the deposits of victims of the Holocaust.
He claims that his latest case makes the "exact" same allegations as the suits that were filed on behalf of holocaust victims.
South Africa's AngloGold and De Beers, the UK's Barclays Bank and Germany's Daimler Chrysler are among the multinational firms already facing apartheid lawsuits.