he makes his living selling tin and tantalum to international companies. in 2010 he warned that the dodd- frank law would backfire... but he says he was up against a powerful lobby. >> imagine that you have angelina jolie at your door. you are a very big u.s. company, george clooney at your door saying you guys, you're the ones fueling the armed groups there. do you think that for the reputation of those companies they would be still sourcing from this region? they said ok we are stopping and that's what happened. >> soon after the law passed, companies took their business elsewhere. sales of tin ore from this province plummeted by more than 90%. >> ah the containers. >> that's the material ready to be exported. we are doing almost 2 containers while we used to do 8 containers per month. >> the only way john, or anyone in congo -- can now legally export to the u.s. is by opting into a system that traces the origin of the minerals. >> yes i can show you some. these are the tags. >> so these tags are attached to the bags of minerals that come here? >> yes. >

tantalum, tungsten, tin, and gold have all been linked to violence in eastern congo by rebel groups and congolese army. >> millions of people haee

tantalum, tungsten, tin, and gold have all been linked to violence in eastern congo by rebel groups and congolese army. >> millions of people have been ki

tantalum, tungsten, tin, and gold have all been linked to violence in eastern congo by rebel groups and the congolese army. >> millions of people have been killed in the congo over the

tantalum, tungsten, tin, and gold have all been linked to violence in eastern congo by rebel groups andthe congolese army. >> millions of people have been killed in the congo over the past decade.