As vice president, Dick Cheney was a prime architect of the worldwide torture regime implemented by the U.S. government (which extended far beyond waterboarding), as well as the invasion and destruction of Iraq, which caused the deaths of at least 500,000 people and more likely over a million. As such, he is one of the planet's most notorious war criminals.
President Obama made the decision in early 2009 to block the Justice Department from criminally investigating and prosecuting Cheney and his fellow torturers, as well as to protect them from foreign investigations and even civil liability sought by torture victims. Obama did that notwithstanding a campaign decree that even top Bush officials are subject to the rule of law and, more importantly, notwithstanding a treaty signed in 1984 by Ronald Reagan requiring that all signatory states criminally prosecute their own torturers. Obama's immunizing Bush-era torturers converted torture from a global taboo and decades-old crime into a reasonable, debatable policy question, which is why so many GOP candidates are now openly suggesting its use.