IN THE 1970s, Abdul Qadeer Khan worked at a European atomic research lab from which he allegedly acquired designs for gas centrifuges to enrich uranium. He then returned to his native Pakistan to became a true national hero as the father of the first Islamic nuclear bomb.
Last week, Mr. Khan went on Pakistani TV with an admission that would have stunned the world had it not been long suspected: For 15 years, he has run a Nuke-Mart, the key source for a global black-market network delivering nuclear equipment, technology, designs and even turn-key packages to Libya, Iran and North Korea.
His admission, and his immediate sham pardon by Pakistani President Pervez Musharraf, underscores the fragility of the Pakistani state and the deep U.S. compromise in buying an alliance with Mr. Musharraf against Taliban remnants and other Islamic fundamentalists. Few believe Pakistan's claim that Mr. Khan acted without the assent and aid of its military, and his pardon may well have been his price for his silence on that particular matter and for his further, very much needed cooperation on the rest of his story.
The U.S. government's public praise for Pakistan's weak response speaks to the primary need to shore up Mr. Musharraf against rising Pakistani Islamists, for whom the fall of Mr. Khan was nothing less than a U.S. conspiracy to humiliate their nation and strip it of its nuclear capacities. Far worse than endorsing this likely cover-up is the prospect of Pakistan's arsenal under the control of these fundamentalists, who have wide domestic support and who twice recently tried to assassinate Mr. Musharraf.
At the same time, while it may be necessary for the United States to engage in such political theater, it's critical that pressures are brought to bear on Mr. Khan to reveal all that he knows about his nuclear sales network. Details revealed so far - suggesting that his dealings may have posed more dangers to America than did Saddam Hussein - are very likely only the start. The United States must learn a lot more from Pakistan, Libya and Iran.
If anything, Mr. Khan's downfall underscores the value of acting on such intelligence. A Libyan tip led to the diversion last October of a German ship bound for Libya from Dubai. On that ship, investigators found centrifuge parts - a discovery, along with other findings inside Libya, that opened the trail back to Mr. Khan.
And that ship-boarding was the first victory under the Bush administration's new Proliferation Security Initiative, an 11-nation agreement last year to interdict planes and ships suspected of carrying banned weapon or missile technology - a move initially cast as largely an effort to stop potential proliferation by North Korea.
The key question now is not Mr. Khan's fate but how to stymie his would-be successors, in Pakistan or elsewhere. His access to national assets was such that he may turn out to be a unique case, but there's no end to the worldwide greed driving such clandestine trading. Mr. Khan was caught not because of international nuclear controls - would that were the case - but because of intelligence (good intelligence, for once) backed by enforcement.