He was a student in London at the time, and there was "no derogatory information that would have prevented him from getting a visa, " the official said.

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The memo went out earlier this week as part of an effort to reform the student visa system, said the official, who spoke on condition of anonymity.

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Tazhayakov was allowed to return to the U.S. from Kazakhstan in January despite not having a valid student visa, a federal law enforcement official told The Associated Press.

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While they have no legal standing or constitutional rights to remain within the country, they may stay provided that the government renews their official visas at the expiration of the previous visa.

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The court also heard that Tazhayakov went to Kazakhstan in December 2012 and was allowed to return to the United States on January 20, despite the apparent lapse in his visa status, the same government official said.

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The official data from the State Department show that L-1 visa approvals went from 35, 896 in Fiscal Year (FY) 2010 to 25, 898 in India in FY 2011, a drop of approximately 10, 000 visas.

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But "the info on him was not deemed specific enough to pull his visa or put him on a no-fly list, " the official said.

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In addition, the official said there was "no derogatory information that would have prevented him from getting a visa" back in June 2008.

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Abdulmutallab was granted a multiple-year, multiple-entry tourist visa at the U.S. Embassy in London in June 2008, the administration official said.

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His student visa status had been terminated because he was academically dismissed from the university, said the official, who was not authorized to discuss the case and spoke on condition of anonymity.

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But "the info on him was not deemed specific enough to pull his visa or put him on a no-fly list, " a U.S. official said.

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"If we pulled his visa or banned him from flying, that would have alerted him you are onto him, " the official said.

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