Fired by the president, the former US attorney has written his first book. He talks about if and when Trump will face justice – and why he fears for his own safety

Preet Bharara is used to dealing with bullies. When he was the US attorney for the southern district of New York, the premier law enforcement body in America, his office prosecuted Osama bin Laden’s son-in-law, Crips and Bloods gang leaders and mafia bosses. For going after the infamous arms dealer Viktor Bout he was banned from Russia, and the Turkish president Recep Tayyip Erdoğan once tried to persuade the then US vice-president, Joe Biden, to sack him (he didn’t). The TV series Billions is loosely based on his legal battles with a hedge-fund billionaire. As he puts it himself: “Neither I nor anyone I know was too afraid to prosecute rich men in suits.”

So when Bharara says that even he is now feeling apprehensive about his personal safety, and that his fears relate not to al-Qaida or the Gambino family, but to the president of the United States, it comes as a jolt. “I used to have great confidence that my government would protect me,” he says. “You understood that if you were an American citizen like me, or resident like Jamal Khashoggi, you weren’t going to be rendered somewhere, you didn’t think that if you travelled to Madrid, say, and a BS red notice was issued for you, you’d be on your own. I’m a citizen of the United States and I served my country for 17 years, yet I don’t have that confidence any more. I don’t know that the government at its highest level thinks of Americans first – it’s whether you are on his side, or not on his side.”

Bharara, 50, has been thinking a lot lately about bullies, and their nemeses – those unsung heroes who strive for what’s right. His first book, Doing Justice: A Prosecutor’s Thoughts on Crime, Punishment and the Rule of Law, takes us back to basics, asking us to reflect on what truth means when a serial liar sits in the Oval Office; what civility involves amid all the social media yelling; and how to uphold the rule of law when thuggish behaviour appears to be the order of the day.

The book is a love letter to the southern district of New York (SDNY) that he led for more than seven years until he was abruptly fired by Donald Trump in March 2017. He praises its spirit of independence – its moniker is “Sovereign District” – and the committed people who work there, such as the “real-life mob-busting cop” Kenny McCabe who took on all five families of the Cosa Nostra.

Facebook Twitter Pinterest Stormy Daniels arrives southern district of New York courthouse for a hearing related to Michael Cohen, April 2018. Photograph: Yana Paskova/Getty Images

As one of the earliest law enforcement agencies in the country, its aligned federal court, known as the “mother court”, has sat continuously since 1789, hearing cases from the sinking of the Titanic to the trial of Julius and Ethel Rosenberg as Soviet spies. The reach of SDNY prosecutors is unlimited. When someone asked Bharara recently to define the agency’s jurisdiction, he replied: “Are you familiar with Earth?”

At its most powerful, Doing Justice works as a metaphorical survival guide for the Trump era. As with everything Bharara does, he writes in a tone that is calm and considered, a warm bath after the outrage of Trump’s daily tweets.

That’s what has made him such an unlikely superstar following his dismissal at Trump’s hands. Since he was ousted from the southern district, he has created a hugely popular podcast, Stay Tuned, exploring the intersection between law and politics, and now has more than 1 million followers on Twitter. “Can you imagine! A former prosecutor has a million Twitter followers – it makes no sense,” he says. “I’m told it’s anxiety, but there’s also a desire to learn from those with experience about what’s going on.”

In the hour I spend with Bharara at his podcast offices in Manhattan, he treats me to the same measured analysis. The style of his conversation is soothing, reassuring, but its content is wholly alarming.

It starts with a phone call he received on 9 March 2017. The president of the United States was on the line, he was told, did he want to take it?

Bharara was puzzled. He’d been summoned to meet the president-elect in Trump Tower shortly after the November 2016 election, when Trump had invited him to stay on at the helm of the SDNY.

Before the meeting ended, Trump asked Bharara for his phone number. That struck the lawyer as odd, though he duly wrote it down on a Post-it note. Now, a few weeks after Trump had been anointed, here he was again on the phone and, against protocol, wanting to talk.

Bharara did not pick up. And he did not call back.

It has been two years since then, and Bharara is still at a loss about why Trump called him. He wonders why, the day after the call, he was told to resign, when Trump had specifically requested that he stay on. (Bharara refused to quit, forcing Trump to fire him 48 hours after his unanswered phone call, on 11 March.) More importantly, he asks himself what that call had been about. What had Trump been after?

“Imagine what it would look like now if I were still US attorney and it became known that I had quiet little chats with the president at the same time we were investigating the Trump organisation and Michael Cohen. So I didn’t call back, and it’s one of the best decisions I ever made.”

I have a great fear that no matter what Mueller says, one half of the American people won’t accept it

Bharara has had no interaction with Robert Mueller’s investigation into possible collusion with Russia during the 2016 election, as the special counsel was appointed two months after Bharara was fired. He has watched the inquiry unfold with detachment but increasing agitation.

He sees Trump’s relentless sniping at Mueller as nothing less than a threat to judicial independence. “The incessant cry of ‘witchhunt’, the constant blurring of the line between politics and law enforcement … A particular person in power doesn’t want to be investigated, and wants to get his supporters to doubt the veracity of the result, so he’s undermining people’s faith, in a direct way, in the rule of law.”

That chipping away at public faith in the law, pumped out through Trump’s Twitter feed – “the biggest megaphone of any human being on Earth”, he calls it – leads Bharara to be deeply fearful of what will happen when Mueller completes his report, as he may any day now.

“I have a great fear that no matter what Mueller says – if it’s a devastating indictment of the president or the opposite – one half of the American people won’t accept it.”

How dangerous would that be? “I think it would be terrible,” he says. “If someone like Bob Mueller, who volunteered to go to Vietnam and took a bullet wound, who held high-ranking jobs then chose to take on lowly homicide cases, if someone of that stature can be attacked and you can make tens of millions of Americans think he is a piece of shit, that’s horrifying to me.”

It’s at this point, just as we are reaching full-blown despair, that we return to the subject of the southern district of New York and its fierce spirit of independence. In his book, Bharara takes us through the fundamental principles of justice and truth that motivate the SDNY’s investigators under the agency’s unwritten mantra: “Do the right thing, in the right way, for the right reasons.”

Drawing on his past cases, he teases out good practice for the rookie prosecutor, as though he were preaching to his own younger self when he joined the SDNY in 2000. He spreads words of wisdom along the way. One of his favourite quotes is from Oliver Cromwell: “I beseech ye in the bowels of Christ, think that ye may be mistaken.”

Facebook Twitter Pinterest Robert Mueller. Photograph: Yuri Gripas/Reuters

While most of the media has fixated on Mueller, the southern district, motivated by such values, has quietly been compiling a devastating case against Trump all of its own. It is not a random fact that the conviction of Michael Cohen, Trump’s lawyer and fixer, for tax fraud and campaign finance violations relating to the pay-off of the adult film actor Stormy Daniels, was secured not by Mueller but by the SDNY.

Bharara, like most informed observers, thinks it highly unlikely that the SDNY will indict Trump while he is still in office. Though there is nothing in the constitution or in law to stop the SDNY from charging Trump, Department of Justice guidelines bar sitting presidents from being prosecuted, and Bharara does not expect to see his former colleagues “going rogue” in that way.

But when Trump leaves office, all bets are off.

The culture of the SDNY is such that if they feel they have sufficient evidence they will definitely go after him when he leaves the White House. “Right is right, and no one’s above the law. That’s not just lip service – the SDNY is steeped in it. No one is above the law: I don’t care who you are, how much money you have, who your friends are.”

Bharara stresses that he has had no inside intelligence about his old stomping ground since he was fired. But when he detects SDNY activity – the boxes of recordings they seized in raids on Cohen’s home and legal office, for instance – it ignites in him his innate pride and confidence in the “Sovereign District” as a bastion against the forces of darkness. “It seems to me that what the SDNY is doing is pulling on a thread. And when the thread is named Michael Cohen, God knows what other things lie ahead.”

• Doing Justice: A Prosecutor’s Thoughts on Crime, Punishment and the Rule of Law by Preet Bharara is published by Bloomsbury (£20) on 19 March. To order a copy go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £15, online orders only. Phone orders min p&p of £1.99.