What might be one of the largest experiments in gun control ever attempted is currently under way in the Colombian capital, Bogota. No weapons are allowed on the streets of this city of 7.3 million people from Wednesday until 30 April. If the ban results in a significant reduction of the homicide rate it might become permanent. The ban is being introduced by a former guerrilla - the city's Mayor Gustavo Petro. "People who own guns legally can still keep them at... (GunPolicy.org)