The 1996 law, which shields European businesses from US penalties, has never been used.
The present sanctions were reinstated after US President Donald Trump withdrew from the 2015 “Iran deal” earlier this month.
The EU signatories to the deal did not withdraw from the agreement, and are working to preserve the deal. On Sunday, French Foreign Minister Jean-Yves Le Drian said his country believes the deal can prevent Tehran from acquiring nuclear weapons.
EU foreign policy chief Federica Mogherini will meet next week with the foreign ministers of Iran, Britain, France and Germany to discuss the various options.