Required reading: US gun control

New legislation in South Dakota will allow teachers to carry guns in school. So what's behind the US's complex relationship with the right to bear arms?

South Dakota has become the first state in the US to pass legislation explicitly allowing teachers to carry firearms in schools. The new law comes amid an intense national debate on guns access after a spate of shootings, including one in which 20 first graders died at Sandy Hook Elementary School in Newton, Connecticut.