The case against a Turkish banker accused of taking part in a scheme to help steer Iranian money around American sanctions has raised questions about the reach of a U.S. statute that can be used to impose criminal penalties on foreigners acting abroad.

The charges against Mehmet Atilla, a former deputy CEO of Halkbank, a state-run bank in Turkey, include conspiracy to violate the International Emergency Economic Powers Act (IEEPA) in relation to a scheme to launder Iranian gas and oil proceeds through the gold trade.