New Delhi, April 15 -- THE WORLD stands on the brink of a nuclear-arms race. If one can be avoided, a big reason will be this: currently, the first country to start such a race risks paying a terrible price. Rogue states caught sprinting for a bomb face crippling sanctions and military strikes. Meanwhile, any halfway respectable country that flouts the Non-Proliferation Treaty-a legal ban on the creation of new nuclear-armed powers, signed by 191 states-risks becoming a pariah, with unknowable economic and diplomatic costs.

Less happily, if a nuclear-arms race does get under way, it will carry on, like toppling dominoes. That is not this columnist's breathless judgment. It is the view of the world's nuclear police chief, Rafael Mariano G...