President Donald Trump is reportedly contemplating pardoning family members, staffers and even himself for connections to the Russia investigation. The story, which was reported by the Washington Post, led to criticism.

But if Trump follows through with a pardon relating to the investigation, it would not be the first time in history a president has created controversy using the constitutional power.

Here’s a run-through of notable, controversial pardons:

1. President Richard Nixon

Which president pardoned him? Gerald Ford

What was he pardoned for? His crimes relating to the Watergate scandal. President Ford issued a preemptive pardon for Nixon because he had not yet been charged with a crime.

Why was it controversial? Ford pardoned Nixon because he wanted the nation to move past Watergate and felt that a president under trial “would be cruelly and excessively penalized.” But many Americans were upset that Nixon was not tried. Some also speculate that Nixon was pardoned as part of a quid pro quo deal with Ford, though there was never any evidence for this. Ford lost the next election.

2. Marc Rich

Which president pardoned him? Bill Clinton

What was he pardoned for? His 65 criminal charges including tax evasion, racketeering, and illegal oil deals with Iran. Rich fled the United States to escape serving consecutive life prison sentences in 1983. Rich was also placed on the F.B.I.’s most wanted list for his crimes.

Why was it controversial? Rich’s ex-wife, Denise Rich, was a major donor for the Democratic Party. Critics argued that Clinton’s decision to pardon Rich was influenced by the donations Denise made. In 2005, the F.B.I. concluded that the donations were not a quid pro quo. A week before the 2016 election, the controversy made headlines when a long-dormant F.B.I. Twitter account released the files detailing the investigation. Some argued that the timing of the release was inappropriate given how close it was to the election.

3. Former Chief of Staff to the Vice President Scooter Libby

(He was technically not pardoned, but instead had his 30-month prison term commuted. A commutation is different from a pardon in that it wipes the person’s sentence, not their record.)

Which president commuted him? George W. Bush

What was he guilty of? He was found guilty of perjury, obstruction of justice and providing false statements to the F.B.I. in the probe of the leaked identity of a CIA operative.

Why was it controversial? Democrats argued Bush abused his power and the judicial system to protect a fellow administration member. Libby was the highest-ranking official to be convicted of a felony since the Iran-Contra affair. The move also came at a time when Bush’s popularity was extremely low, possibly exacerbating the public outrage to the pardon.

4. Former Secretary of State Caspar Weinberger

Which president pardoned him? George H.W. Bush

What was he pardoned for? Lying under oath to the independent counsel investigating the Iran-Contra affair.

Why was it controversial? Bush pardoned six government officials involved in the scandal, including Weinberger. Weinberger was the highest profile of the six that Bush pardoned. The investigation essentially ended the probe being conducted by the independent counsel.

5. Vietnam draft dodgers

Which president pardoned them? Jimmy Carter

What were they pardoned for? Dodging the draft during the Vietnam War.

Why was it controversial? The pardon was a campaign issue in the presidential race between Carter and then-President Ford. Carter promised to deliver an outright pardon to all draft dodgers that had avoided service by leaving the country or not registering. Ford, on the other hand, said he would only give a conditional amnesty. Carter issued the pardon on his first day in office. Many Americans were critical of Carter’s decision, especially veterans.

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Write to Jack Brewster at jack.brewster@time.com.