There was a time when Rudy Giuliani was a sort of “Shell Answer Man” for ethics. Like the man who answered questions about driving in the oil-company commercials, Giuliani was the authoritative voice in New York on ethical standards in politics and finance. As the U.S. attorney in Manhattan in the 1980s, he had the power to back up his call for raising ethical standards and was nationally celebrated for his cases against crooked Wall Streeters, corrupt politicians, and mobsters.

When he ran for mayor of New York City, raising the level of ethics in government became the cornerstone of his campaign. He called for ethics to be better taught in law and business schools, and in elementary schools as well. He recommended that Greek philosophy be taught in high schools. “Institutions—such as the family, the church, and the community—that we used to rely on to teach ethics at an early age…aren’t as readily available for our children, whether they're poor, middle-class, or wealthy,” he said in an interview with New York’s Newsday.

Three decades later, Giuliani is defining ethical deviancy downward in an attempt to protect his legal client, President Donald Trump. In a December 2 tweet, Giuliani derided special counsel Robert Mueller for bringing “process cases”—cases that involve lying in sworn testimony or in interviews with federal agents. He pointed to lawyer Michael Cohen’s guilty plea to making false statements to Congress as an example of a “process case,” explaining, “These cases, and all so far, demonstrate no evidence of Trump collusion.”

Giuliani brought a few “process cases” himself when he was a prosecutor. One involved a twenty-something low-level trading assistant in the Beverly Hills office of Drexel Burnham Lambert, Inc., an investment bank Giuliani chased like Captain Ahab going after Moby Dick (except that the company went down). The trader, Lisa Jones, said Giuliani’s investigators tried to bully her into cooperating; there was no allegation that she took part in any fraud. Still, she was sentenced to eighteen months in prison, with no parole.

For those who cooperated with Giuliani, the story was much different. He allowed financial fraud kingpin Ivan Boesky to plead guilty to a “process charge,” one count of making false statements to the Securities and Exchange Commission, in exchange for his testimony. Kingpin Boesky, who implicated Drexel, served just twenty-two months in prison.

Giuliani also used perjury and obstruction of justice to get steeper sentences in insider-trading cases, which judges had treated with leniency. Judges generally take perjury and obstruction convictions very seriously, as Giuliani knew.

If Giuliani really believes it’s meaningless that Trump’s former right-hand man lied to Congress in hopes of derailing an investigation of the president, then he’s lost his ethical compass. One can only imagine how Giuliani the prosecutor would have handled the scenario described in the charge Cohen pleaded guilty to.  It says that acting on Trump’s behalf, Cohen worked with “Individual 2”—identified as Felix Sater, a convicted, mob-linked felon with extensive contacts in Russia—through the first half of 2016 to try to push a Moscow development project at the highest levels of the Russian government, even as Trump was campaigning for the presidency. It adds that Cohen discussed the project “multiple times” with “Individual 1”—Trump, “and he briefed family members of Individual 1 within the company about the project.” And then Cohen lied to Congress about what happened “in hopes of limiting the ongoing Russia investigations.”

During the same time period, the Trump campaign had learned through campaign aide George Papadopoulos that the Russian government had “dirt” on Democratic candidate Hillary Clinton in the form of “thousands of emails.” Papadopoulos admitted to lying to federal agents about that.

Whether Trump and his family intersect with any of this remains to be seen, but it’s a matter of utmost importance. Even if there is insufficient credible evidence to charge that Trump took part in the “conspiracy to defraud the United States” —Mueller’s charge against Russian intelligence operatives who hacked Democratic National Committee computers—Trump would be vulnerable to impeachment if he’s implicated in lies told under oath.

That’s the case Giuliani is battling.