CARLOS BARRIA/REUTERS

US President Donald Trump has reportedly asked lawyers to investigate his authority to pardon himself and members of his own family over the ongoing investigations into collusion with Russia.

ANALYSIS: "When the president does it, that means it is not illegal," former US president Richard Nixon said during a televised interview in 1977. But Nixon understood that he could never pardon himself. Current US President Donald Trump may not.

Four of of the best-sourced journalists in Washington reported on Thursday night (Friday NZ Time): "Some of President Trump's lawyers are exploring ways to limit or undercut special counsel Robert S. Mueller III's Russia investigation, building a case against what they allege are his conflicts of interest and discussing the president's authority to grant pardons, according to people familiar with the effort.

"Trump has asked his advisers about his power to pardon aides, family members and even himself in connection with the probe, according to one of those people," Carol D. Leonnig, Ashley Parker, Rosalind S. Helderman and Tom Hamburger wrote in The Washington Post.

AARON P. BERNSTEIN/REUTERS

Special counsel Robert Mueller's probe into Russia's election meddling appears likely to include some of the Trump family's business ties.

"A second person said Trump's lawyers have been discussing the president's pardoning powers among themselves. Trump's legal team declined to comment on the issue. But one adviser said the president has simply expressed a curiosity in understanding the reach of his pardoning authority..."

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Reports suggest Trump has been "fuming" about the Mueller probe "as he has been informed about the legal questions that he and his family could face".

He is reportedly upset that the investigation could move to scrutinise his deal-making and tax returns.

The US Constitution does not explicitly prohibit a president from pardoning himself, but experts say a pardon is something you can only give to someone else.

A common-law canon that prohibits individuals from serving as a judge in their own case is a "fiercely debated but unresolved legal question," according to Brian C. Kalt, a constitutional law expert at Michigan State University who has written extensively on the question.

This is the same ethos that was on display when Trump boasted to Access Hollywood host Billy Bush in 2005 that he could get away with kissing, groping and propositioning married women.

"When you're a star, they let you do it," Trump said on a hot mic. "You can do anything."

He won despite the emergence of that video. Most Republican leaders quickly moved on.

Trump often acts like a man who has learned over his 71 years it's better to ask forgiveness than permission. When he fired James Comey as FBI director, which he admitted he did with the Russia investigation on his mind, he was caught off guard by the blowback. Perhaps it was partly because he's accustomed to being able to get his way.

Soon after the November election, Trump flippantly brushed aside a question about the conflicts of interest that would inevitably arise from his business dealings. "The law's totally on my side. The president can't have a conflict of interest," Trump said in one of his most Nixonian turns of phrase (and there have been many). "In theory, I could run my business perfectly and then run the country perfectly. There's never been a case like this."

Defending his refusal to divest from his complicated holdings, he said voters knew what they were getting when they voted for him. "Prior to the election it was well known that I have interests in properties all over the world," Trump tweeted during the transition.

Running the privately held Trump Organization, the president was not accountable to an independent board of directors. No-one could fire him for making disastrous decisions because it was a family business. (Every time I write about Trump's background in business, former chief executives at Fortune 500 companies complain to me that Trump didn't have to deal with boards and audits the way they had to. . .)

When he took office six months ago, Trump himself now acknowledges that he did not understand the limitations of a president's power to exert his will on the federal government. But it's also pretty clear he still does not understand it.

In his sit-down with the New York Times in the Oval Office on Wednesday, Trump dubiously asserted a prerogative to order an FBI director to end any investigation for any reason at any time. He said he had the right to tell Comey to stop looking into Michael Flynn, though he continues to insist he did not do that. "Nothing was changed other than Richard Nixon came along," Trump said. "Out of courtesy, the FBI started reporting to the US Department of Justice. But there was nothing official. There was nothing from Congress... But the FBI person really reports directly to the president of the United States, which is interesting."

CNN reported overnight that Trump personally interviewed his nominee to be US attorney for the District of Columbia before tapping her. There are 93 presidentially appointed US attorneys, but this one is of special interest to Trump because she has jurisdiction over the capital city - where he obviously has a lot of personal interests at stake.

"Jessie Liu, the current deputy general counsel for the Treasury Department who Trump tapped to be the next US attorney for the District of Columbia, disclosed in her responses to the Senate Judiciary Committee that she met with the President as part of her interview process," Laura Jarrett scooped:

"According to multiple former US attorneys and several law enforcement sources ... such a meeting with the president as part of the interview process would be virtually unheard of in past administrations... Of the first seven US attorney nominees that Trump selected in June, only Liu said that she met with Trump. Other nominees described only meeting with Justice Department officials, such as Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein, in their submissions."

Former US president Barack Obama did not meet with his picks to lead the District's US attorney's office in 2009 and 2015 before their nomination.

"It's wrong, and the reason it's wrong is that it serves to undermine the rule of law," Joyce Vance, former US attorney for the Northern District of Alabama, told CNN.

"This goes to the independence of the Justice Department" and "any effort by any president to diminish that is problematic".

This is a big dang deal that should not get lost amid the even bigger stories. It raises a host of questions about what commitments Liu might or might not have made to the president and to what extent she would try to protect him once confirmed.

 - The Washington Post