What Justifies Military Intervention?

The decision by the US, France and Britain to bomb Syria after seeing evidence that President Bashar al-Assad had allegedly used chemical weapons on civilians has divided the international community. Are we living in a world where might, not right determines how states behave, or is a more moral legal framework in the process of being born? This week on the Real Story, Carrie Gracie and a panel of expert guests ask what can justify attacking another country.