Can Iran be stopped?

IN 2009 Iran was on the verge of electing a reformer as president. Ayatollah Ali Khamenei, the supreme leader, subverted the vote and crushed the ensuing protests. Last week the same desire for change handed a landslide victory to Hassan Rohani—and Mr Khamenei hailed it as a triumph.

When a country has seen as much repression as Iran, outsiders hoping for a better future for the place instinctively want to celebrate along with all those ordinary Iranians who took to the streets. The smiling Mr Rohani’s public pronouncements encourage optimism, for he sounds like a different sort of president from the comedy-villain, Mahmoud Ahmadinejad, who precedes him. Yet even if his election bodes well for Iranians, it does not necessarily hold equal promise for the rest of the world. Iran’s regional assertiveness and its nuclear capacity mean that it is a more dangerous place than it ever was before.