Before receiving a full pardon from President Trump on charges of fraud and obstruction of justice last week, former media mogul Conrad Black enlisted one of Trump’s biggest on-air defenders, Alan Dershowitz, to get the president’s attention.

Dershowitz — a Harvard law professor who has regularly gone on television to declare Trump’s innocence of obstruction of justice charges — said he wrote a letter to the White House requesting the pardon.

Dershowitz’s letter, which was reviewed by the White House Counsel’s Office, played a major role in getting Trump and his legal advisers on board, according to Black, a Canadian billionaire and former Trump business partner who wrote a glowing book about the president last year.

“Some people are representing that it was a ‘back-scratching’ job — that I write nice things about the president, and he gives me a pardon,” Black said in an interview this week. “But [Trump] said he always thought it was a bad rap, and the White House legal confirmed that and said it was.”

The White House said singer Elton John, radio host Rush Limbaugh and former secretary of state Henry Kissinger also advocated on behalf of Black.

The unconventional sequence of events that led to Black’s pardon highlights the haphazard approach Trump has taken to using one of the most absolute powers of the presidency.

Often without consulting the Justice Department, Trump has pardoned a range of political allies and vocal supporters. He has freed a woman whose case he learned about from celebrity Kim Kardashian, pardoned former Arizona sheriff Joe Arpaio after promising to do so at a political rally and granted clemency to several people after learning of their cases on Fox News. On the same day he pardoned Black, he granted clemency to Patrick J. Nolan, the former Republican leader of the California State Assembly and a friend of Trump’s son-in-law and adviser, Jared Kushner.

Special counsel Robert S. Mueller III also documented that Trump and his lawyers repeatedly suggested he might pardon some of his former aides who were convicted of felonies during the probe into Russian interference in the 2016 U.S. election.

Dershowitz, who said he did not know Black well, said he talked about his case with Kissinger before using his clout with the Trump administration to get a letter through to the president’s inner circle. That clout has grown significantly since 2017 as the longtime Democrat has become an informal adviser to the president and a fixture on cable news.

Trump has frequently quoted Dershowitz’s defenses as he has faced legal scrutiny during Mueller’s investigation into election interference and obstruction of justice.

“Pardons are designed for cases like this — to ameliorate harsh sentences. Sentences today are too harsh,” Dershowitz said. “A pardon is an apt mechanism to reduce injustice.”

Black, who owned a media empire that included Canada’s National Post, Britain’s Daily Telegraph, the Chicago Sun-Times and the Jerusalem Post, was convicted in 2007 on fraud charges, including alleged embezzlement and obstruction of justice.

He served more than three years in prison and was deported to his native Canada after he was released in 2012.

In announcing the pardon last week, White House press secretary Sarah Sanders said the U.S. Supreme Court “largely disagreed” with prosecutors “and overturned almost all charges in his case.”

In fact, in a unanimous decision delivered by Justice Ruth Bader Ginsburg in 2010, the Supreme Court threw out Black’s conviction on two fraud charges because the jury had been given unclear instructions, but it left untouched his conviction for obstruction of justice.

After the case was sent back to the lower court to be reconsidered, Black’s convictions on two counts were upheld, and he was returned to prison.

Black did not apply for the pardon through official Justice Department channels, which largely have gone unused as Trump has issued pardons to people who have praised or supported him. Black was the 10th person to be pardoned by Trump.

Dershowitz said he sent a letter to the White House a few months ago by email and did not hear back. But Black said the White House legal team reviewed the letter from Dershowitz about his case and agreed “it was an unjust verdict.” A White House spokesman did not respond to requests for comment.

Defense attorney Ron Safer, who served as a lawyer to one of Black’s colleagues, also wrote a letter to the White House in support of a pardon for Black.

During a phone call earlier this month with Trump, Black said he asked for permission to repeat that the president felt the verdict was unjust. Trump first said, “I think so.” He later agreed after consulting with White House Counsel Pat Cipollone, who was standing nearby, Black said.

In a book published last year, titled “Donald J. Trump: A President Like No Other,” Black praised Trump’s “confidence to affront tradition” and “genius for spectacle.”

Black and Trump had previously done a business deal together, collaborating on the sale of the former Sun-Times building. Trump ultimately developed the building on the Chicago River and built a hotel. Black, 74, also said the two men have long been friends.

Before their conversation earlier this month, which Black said was like old times, Black said the two men had not spoken since Trump had been sworn in to office

“With him, you take up where you left off. He doesn’t change much,” he said of Trump. “It’s as if you were talking last week but in fact it was years before.”

Black said he drew a link between his case and the president’s legal challenges.

“I suggested that he knew ‘better than anyone’ the antics of some U.S. prosecutors,” Black wrote in his account of Trump’s call in the National Post, a Toronto-based newspaper.

Black’s legal predicament has at least one similarity to Trump’s experience with the Mueller investigation. Black and Trump have argued that obstruction of justice charges should not be considered if no underlying crime has been committed.

After Black learned that federal authorities had launched a fraud investigation, he “removed 13 boxes of documents from his office” — an act that was caught by parking-garage video cameras, then-Solicitor General Elena Kagan wrote for the government in a Supreme Court brief. A jury found him guilty of obstruction of justice for removing the boxes after investigators asked for documents.

Black’s lawyers argued before the Supreme Court that a reversal of his fraud charges should automatically lead to a dismissal of the obstruction charges.

Kagan — who has since become a Supreme Court justice — pushed back on that theory, arguing “the obstruction count did not require proof that Black committed the crime under investigation; it required only that the concealment of records had the purpose of subverting an official proceeding.”

Mueller’s investigation found 10 potential instances of obstruction of justice by Trump, even as the special counsel did not establish an underlying crime of conspiracy in Russia’s election interference effort.

As some Democrats call for an impeachment inquiry over obstruction and other charges, Trump and his allies have argued that the lack of an underlying crime means that obstruction of justice charges don’t apply.

“How can you have Obstruction when not only was there No Collusion (by Trump), but the bad actions were done by the ‘other’ side?” Trump tweeted earlier this month. “The greatest con-job in the history of American Politics!”

Black said Trump told him the pardon had nothing to do with the nice things he has written about the president. He described his book as “thin” given that Trump has not been in office long.

He said he plans to update the book with a second edition.

Marc Fisher contributed to this report.