The Supreme Court heard arguments Tuesday about whether U.S. chocolate companies should be held responsible for child slavery on the African farms from which they buy most of their cocoa.

Six African men are seeking damages from Nestlé USA and Cargill, alleging that as children they were trafficked out of Mali, forced to work long hours on Ivory Coast cocoa farms and kept at night in locked shacks. Their attorneys argue that the companies should have better monitored their cocoa suppliers in West Africa, where about two-thirds of the world’s cocoa is grown and modern day slavery in the form of child labor is widespread.