Qatada was not initially regarded as a domestic threat – indeed, MI5, the British security agency, attempted to consult with him more than once for better understanding of the country's Islamist community. But by the end of the 1990s, the British government had begun to revise its opinion of Qatada, who had become even more vocally hardline, targeting Jews in his sermons and speaking out in favor of suicide attacks.
At the same time in Jordan, Qatada was charged and convicted in absentia for several terrorism-related crimes. In 1998, he was sentenced to death for supporting attacks on foreign targets in Jordan, though his sentence was quickly commuted to life in prison. And then in 2000, he received a 15-year sentence for supporting similar attacks against tourists attending Jordan's millennium celebrations. Jordanian prosecutors said he provided backing for both operations from Britain.
Following Sept. 11, 2001, Britain enacted laws empowering the government to detain terrorism suspects without charge. Qatada, whose teachings were said to have influenced both Zacarias Moussaoui, the "20th 9/11 hijacker," and "shoe bomber" Richard Reid, was by then a clear concern for the United Kingdom. Although initially able to avoid capture, he was arrested in October 2002. Since then, Qatada has been in and out of jail pending his deportation to Jordan, though he denies supporting terrorism.
The short answer is that Jordan's case against Qatada appears too dependent on evidence extracted via torture.