The United States does not torture, Barack Obama has proclaimed on numerous occasions since he arrived at the White House and almost immediately signed an executive order banning controversial interrogation techniques. The lingering, perhaps trickier, question is what to do about prisoner abuse that may have occurred in the seven years before Mr Obama was elected president.

That question was partially answered when Eric Holder, Mr Obama’s attorney general, launched an investigation into the interrogation of detainees held by the Central Intelligence Agency during the administration of George Bush. Called a “preliminary review”, the limited probe gives a second look at specific interrogations that may have overstepped even the more lenient legal guidance of Bush-administration lawyers. The review will determine if a full investigation is warranted.

Despite the narrowness of its stated scope, the investigation has drawn passionate criticism from Republicans, notably Dick Cheney, the former vice president, who says the probe is outrageous and will make the country less safe.

“It’s clearly a political move,” Mr Cheney told Fox News last Sunday, adding that he believes the review will expand beyond the individual interrogators involved. “There’s no other rationale for why they’re doing this.”

Mr Cheney said he stands by interrogations conducted while he was in office – even those that went beyond what the legal interpretations at that time allowed. “Enhanced interrogation techniques were absolutely essential in saving thousands of American lives and preventing further attacks against the United States,” he said. “It was good policy.”

These arguments have reignited debate over torture and caused some liberals, such as Jarold Nadler, a Democratic congressman from New York, to call for an expansion of the new probe to include Mr Cheney himself.

“Former vice president Cheney is essentially saying that any acts performed by members of the CIA – no matter how illegal or abhorrent – are OK, and must never be the subject of a criminal investigation,” Mr Nadler said in a statement issued this week. “This is outrageous, and violates just about every traditional American concept of liberty and justice.”

Robert Gibbs, the White House press secretary, dismissed Mr Cheney’s claim that the review will devastate the morale of the intelligence community: “I’m not entirely sure that Dick Cheney’s predictions on foreign policy have borne a whole lot of fruit over the last eight years in a way that has been either positive or, to the best of my recollection, very correct,” he said on Monday.

The Democratic National Committee later in the week released an anti-Cheney television ad, which shows the former vice president making statements that turned out to be incorrect, such as, “There is no doubt that Saddam Hussein now has weapons of mass destruction”. Weapons of mass destruction were not found in Iraq. Mr Cheney’s final statement in the commercial was taken from the Sunday interview in which he supported “enhanced interrogation techniques” – a stance the ad says is also wrong.

The US public is hardly of one mind on the issue of torture. An Gallup poll in April found 51 per cent of Americans wanted an investigation into the harsh interrogation techniques used on suspected terrorists during the Bush administration, while 42 per cent opposed such a probe.

Mr Holder announced his preliminary review in late August, on the same day the government, under a long-delayed court order, declassified parts of a 2004 CIA report with fresh details of harsh interrogations, including a mock execution, suggestions that a detainee’s mother would be sexually assaulted in front of him and intimidation with a power drill and a handgun. It is unclear if the probe covers these incidents or is limited to cases that have not been made public.

Mr Holder added the new cases to the mandate of John Durham, a widely respected career prosecutor who was appointed by Michael Mukasey, a Bush-era attorney general, to look into another matter involving the CIA. Mr Holder said his decision to initiate the limited investigation was based on information in the unredacted version of the 2004 CIA report, the recommendations of a separate justice department review and “other relevant information”. He described the review as “the only responsible course of action for me to take”.

Charles Stimson, a justice department official under Mr Bush and senior legal fellow at the Heritage Foundation, a conservative think-tank, said the investigation makes sense if new information has come to light that was not available to or uncovered by the lawyers who previously reviewed the cases.

“Typically prosecutors don’t look back over other career prosecutors’ work, but it does happen,” he said. “But it’s an awkward and potentially dangerous precedent to go back and review decisions by a career prosecutor on a sensitive and controversial issue. If there’s no additional information, then it is a raw political act.”

Mr Obama has so far avoided directly answering questions about prosecuting Bush-era officials – particularly lawyers who backed questionable techniques, such as waterboarding, with problematic legal opinions. “We should be looking forward and not backwards,” he has said on numerous occasions.

Reports have suggested Mr Holder was acting on his own in launching the probe that appears to buck the wishes of his boss, though critics, such as Mr Cheney, charge that the administration is faking any disagreement between the White House and the justice department to help the president distance himself from the contentious issue.

Ken Gude, a national security analyst at the Center for American Progress, a progressive think-tank, thinks Mr Holder’s difficult decision to launch the investigation was “the opposite of politics”.

“The politically expedient choice would have been to follow what the president wants,” he said. “Certainly there are a number of Democrats who are uneasy with investigating the CIA. The political choice would have been to do nothing.”

A recent batch of presidential pardons has rekindled debate in the United States about whether George W Bush, the president, will, or should, preemptively grant amnesty to people involved in harsh interrogations – and arguably torture – of suspected terrorists.

Several major newspaper editorials and numerous Democratic legislators and legal scholars have in recent days urged the president against defensively forgiving departing and former administration officials who have not been prosecuted for their activities during the “war on terror”, but could be in the future.

“The only practical way of ensuring the executive is staying within the rule of law is to have the possibility and the threat of prosecution available against the people who carry out his orders,” said David Golove, a law professor at New York University. “If you don’t have that threat then you lack any sort of incentive to uphold the rule of law.”

Others argue that talk of such blanket amnesty would be unnecessary if Democratic legislators were not calling for criminal prosecutions of Bush administration employees. They say while policy disagreements are common between administrations and political parties, sending one’s predecessors to jail would be a bad precedent.

“It would be disastrous if they were to do that,” said PS Ruckman Jr, a political scientist at Rock Valley College in Illinois who runs a blog on pardon powers. “It’d be a pretty big can of worms to open.”

Mr Bush last week reduced the sentences of two men imprisoned on drug-related charges and pardoned 14 others. His White House secretary said there was a high probability there would be further pardons before Mr Bush leaves office, but would not elaborate.

The incoming administration of Barack Obama has not signalled any intent to prosecute people involved in interrogations. The Associated Press reported last month that two unnamed Obama advisers said there was little, if any, chance the new administration would take legal action.

Brooke Anderson, a spokeswoman for Mr Obama, recently said decisions about interrogation issues will not be made until the new administration’s full national security and legal teams are in place. She had no update this week after Mr Obama announced his nominations for key national security positions, including the attorney general.

Mr Golove and others noted that the Military Commissions Act passed by Congress in 2006 would probably protect anyone who approved or used at least some of the controversial interrogation techniques – including waterboarding, a form of simulated drowning.

“It’s really not clear that it’s going to be legally possible to prosecute people,” Mr Golove said. “There’s a bit of a point of unreality” in this debate.

Experts agree any such clemency, if granted at all, would not apply to soldiers already convicted of using illegal methods to abuse “low-value” detainees at the Abu Ghraib prison in Iraq, the detention centre at Bagram Air Base in Afghanistan and elsewhere.

Reversing the impression left by such notorious incidents will require bold action from Mr Obama, said Khaled Abou El Fadl, a law professor at the University of California in Los Angeles who specialises in national security law. Mr Fadl, a former Bush appointee to the US Commission on International Religious Freedom, said the new administration must break absolutely from practices criticised as torture with firm directives to the military and the Central Intelligence Agency.

Mr Obama must “as a matter of policy and cultural attitude be very clear… that the United States’ commitment to liberal democracy and human rights is, above all considerations, a fundamental part of our national security and national identity”. Pardons for possible torture would send the wrong message, he said.

The US constitution grants the president power to forgive any federal crime besides his own impeachment and the Supreme Court has interpreted this broadly to include the ability to preemptively pardon individuals before legal proceedings have started.

The power was famously exercised a month after Richard Nixon resigned as president in 1974 amid the Watergate corruption scandals. His replacement, Gerald Ford, pardoned him for crimes against the country he may have committed during his time in office although no specific indictments had been handed down.

Mr Bush could grant pre-emptive pardons to individuals within his administration or to an entire class of people – anyone who approved or used interrogation methods during his two terms, for instance.

His White House, however, “isn’t inclined to grant sweeping pardons” for officials involved in the interrogations, the Wall Street Journal reported late last month, citing multiple unnamed sources.

The report hedged however, saying Mr Bush’s position could still change.

One concern is that such amnesty would essentially be an admission the people it covers broke the law. White House officials have said the practice of waterboarding, for instance, was legal when it was used, although the director of the CIA has said he banned the technique in 2006.

Rock Valley College’s Mr Ruckman, however, said presidential pardons do not necessarily imply guilt.

Those who favour a blanket amnesty argue it would remove any likelihood of a legal investigation prompted by subsequent findings. Also, anyone receiving a pardon would have to give up their constitutional right to refuse to give testimony that might incriminate them – and this might encourage them to speak frankly if a truth commission were convened.

Although the constitution specifically says “Congress may not restrain the president’s power to pardon”, numerous Democratic legislators have come out publicly against amnesty for those involved in interrogations as well as surveillance activities.

Jerrold Nadler, a Democratic congressman from New York, last month introduced a bill calling on Mr Bush to refrain from preemptively pardoning senior administration officials.

Ilan Kayatsky, a spokesman for Mr Nadler, said the non-binding resolution is “more of a warning rather than a real attempt to stop him legally”.

Mr Bush has granted a total of 171 pardons during his nearly eight years in office, according to the AP. Bill Clinton and Ronald Reagan each issued more than twice that many in the same amount of time, with Mr Clinton issuing a large number in his last days as president before turning over the White House to Mr Bush and the Republican Party.