THIS has been a banner week for the conspiracy theory that Barack Obama (whose birth certificate can be seen on the right) was not born in the United States, with CNN's pugnacious host Lou Dobbs doing a lot of the promotion. Again and again, on his radio show and on his TV show, Mr Dobbs suggested that the jury was out on whether Mr Obama was born in Hawaii in 1961. Today, the one-man crusade ended with an email from Jon Klein, CNN/US's president, informing producers to knock it off. "I asked the political researchers to dig into the question 'why couldn't Obama produce the ORIGINAL birth certificate?'" wrote Mr Klein. He handed over all of their research and added

It seems to definitively answer the question. Since the show's mission is for Lou to be the explainer and enlightener, he should be sure to cite this during your segment tonite. And then it seems this story is dead—because anyone who still is not convinced doesn't really have a legitimate beef.

This is actually an insight into how conspiracy theories work. They feed off of the conventions of journalism and the legal system. A year ago, when the first sceptics scratched their head about where Mr Obama was born, CNN's producers investigated it. At the same time, John McCain's lawyers investigated it. They found out that Mr Obama was born in Hawaii, but they didn't rush to report it, because, well, it wasn't news. To conspiracy theorists, however, the fact that no one answered their questions in public meant that the questions were unanswerable. Lawsuits against Mr Obama on this issue have fallen flat because they've been frivolous; the conspiracy theorists call that evidence that no one can answer their concerns.