Mr. al-Megrahi, who has been diagnosed with prostate cancer, was freed by the Scottish government on "compassionate grounds" after doctors claimed he probably had only three months to live.
But that was two years ago – a fact that has sparked renewed condemnation among US and British politicians.
Prime Minister David Cameron says it was "wrong" for Megrahi to be released early from his jail term in a Scottish prison, his Downing Street spokeswoman said. Those comments are likely to galvanize calls in the US for him to be extradited from his Libyan sanctuary.
Republican presidential hopeful Mitt Romney said the rebels should turn over Megrahi once they complete the takeover of Libya. Member of the British Parliament Robert Halfon, of Cameron's governing Conservative Party, said he should be "brought back" to the UK, "spend the rest of his life in a Libyan jail," or "be extradited to the US."
At the time of his release in August 2009, many critics of the plan suggested it was being done to secure multimillion dollar oil deals with Libya. But the British and Scottish governments at the time have insisted the decision had been taken by the Scottish Justice Minister Kenny MacAskill.
British officials have already said there appears to be no official mechanism under which he could be brought back to the UK. As the Scottish justice system is independent from that of the rest of the UK, Mr. Cameron's government has no jurisdiction over Megrahi.
What's more, the Scottish government has shown no sign of changing its steadfast position on the matter – one it has maintained since Megrahi's release amid mounting criticism.
A government spokesman said Tuesday he was sent back to Libya "according to the due process of Scots law because he is dying of terminal prostate cancer."
The spokesman added that Scottish authorities are monitoring the former Libyan government agent under the terms of his release license, "which he has not breached."
Scottish officials said this week they were stepping up efforts to make contact with Megrahi. Local authorities here says they have been in regular contact with him via telephone and webcam since his release. Monthly medical reports are sent to Scotland, the authority added.
Talk of attempts to ship Megrahi to the US has elicited a negative reaction in Scotland. In an editorial, leading Scottish national newspaper The Herald said "the calls for him to be extradited for imprisonment or retrial in the US should be resisted by Western powers who preach the importance of transparent application of the law."
It was just before Christmas in 1998 when the American airline Panam's flight 103 was downed over Lockerbie, killing 270 people. It was en route from London to New York, and claimed the lives of all 259 people on board and 11 on the ground after it exploded over the southern town on Dec. 21. Megrahi, the only individual ever convicted in the attack, was jailed in 2001.
Qaddafi's government has admitted Libyan responsibility for the bombing, with the embattled leader agreeing in 2003 to pay compensation to the families of the victims. But he has never admitted personally ordering the strike, despite allegations emerging that he had given the go-ahead.
[ Video is no longer available. ]