The UN's resolution 1540 obliges all governments to stop nuclear (and chemical and biological) bomb-making materials falling into terrorist hands.

ECONOMIST: Preventing nuclear trafficking is easier than policing it

In fact, Libya's effort to concoct an atom bomb never got very far, and its small stock of rudimentary chemical weapons is probably already in the rubbish bin.

ECONOMIST: Libya

The United States and its allies invaded Iraq in March 2003, accusing Saddam Hussein's regime of concealing stocks of chemical and biological weapons, long-range missiles and efforts to develop a nuclear bomb from U.N. weapons inspectors.

CNN: Bush in Ohio defends war

Manholes have been welded shut, bomb-sniffing dogs are a familiar sight, and plans have been drafted for responses to possible chemical or biological attacks.

CNN: Convention unfolds under extraordinary security