He knows better. Or at least he did.

There was the time the lawman charged boxing huckster and longtime Donald Trump partner Don King with hiding his personal income behind his eponymous promotional business to dodge taxes, and tried to send him to jail for 46 years.

The time he went at Roy Cohn for the millions that the Joe McCarthy henchman turned Trump mentor had hidden by pretending that he had no personal income, but only what was memorably described in the Daily News as a “giant untaxable expense account to carry on with the business of being Roy Cohn, celebrity person.”

The time he charged the Manhattan real-estate mogul who’d bragged that “only the little people pay taxes,” and sent the Queen of Mean to prison.

“If you reflect on it, there are very few things that our government asks of its citizens in exchange for all the blessings of living here,” the lawman said: pays taxes and obey the law.

“Unfortunately,” he went on, “there are some wealthy people who do not understand this.”

And the time he ran a TV ad ripping a politician who’d failed to file his taxes in some years and then tried to hide that fact. “Haven’t we had enough with city officials who wait until they get caught to obey the law?” a voice intoned, over a shot of IRS forms. “Think about it. Would you be a candidate for mayor if you didn’t pay your taxes?”

Now, Rudy Giuliani, lawman gone deplorable, is calling Donald Trump “an economic genius” for finding a way to book a clean billion dollars in losses in a single year—incredibly, that’s 2 percent of all the losses reported in all the tax returns in America in 1995, when the economy was humming under a President Clinton.

Like Don King said after he beat Rudy’s rap—and the system, of course, isn’t the only thing he’s beaten—“Only in America.”

Only in America could the guy who famously mocked the city’s Off Track Betting franchise as “the only bookie joint in the world that loses money” call Trump a genius for pissing away hundreds of millions in Atlantic City, and taking down the town and its jobs with him. For finding a way to hand off his losses to investors and contractors and you, dear taxpayer, while keeping all the gains for himself.

And to call him a “genius” days before the last place in town with Trump’s name still on it—The Trump Taj Majhal, now owned by Carl Icahn—is due to close down, leaving dozens of stone elephants outside what will be a colossal wreck. Trump, of course, screwed the guy who made the elephants, way back when, and pretty much everyone else who helped build that monstrosity.

“I am Trump, king of debt. Look on my works, ye mighty and despair.”

We won’t know unless he finally releases his tax returns whether Trump broke the law, or just found a loophole big enough to drive a billion dollars through. What we do know is that Giuliani once knew better.

Research contributed by Brandy Zadrozny.