The family of Michael Flynn this week reignited an ongoing national conversation about the power of presidential pardons, by urging President Donald Trump to clear the former national security adviser’s name.

“About time you pardon General Flynn who has taken the biggest fall given the illegitimacy of his confessed crime in the wake of all this corruption,” the retired lieutenant general’s brother, Joseph, said on Twitter.

The White House offered no official response to the social media exhortation, but Trump has confidently asserted his authority in this arena, tweeting in July that “all agree the U.S. President has the complete power to pardon.”

Presidential pardon power is indeed extensive, but any move Trump took to absolve associates under investigation for aiding Russia’s interference in the 2016 election could come at a steep political—and even legal—cost for the embattled President.

TPM surveyed legal experts about the limits of this power, and how Special Counsel Robert Mueller can work around it.

Presidential pardon power “fairly absolute”

Legal scholars agree that the U.S. president has “fairly absolute” authority to pardon any other U.S. citizen for any federal crime, Fordham University law professor Jed Shugerman said in a phone interview.

“Obviously what he can’t do is take office and say, ‘I pardon everyone in advance for this crime I’m about to run from out of the Oval Office,’” Duke University law professor Lisa Griffin said. “So you can pardon anyone from the time that the offense has been committed. There do not have to be charges pending; there certainly does not have to be a conviction.”

One frequently cited historical precedent is Gerald Ford’s full 1974 pardon of his predecessor Richard Nixon for any crimes committed during his time as president.

There are important exceptions and unsettled areas of the law that come into play with the Russia probe, however.

According to Griffin, extant Justice Department memoranda from previous administrations have bolstered a key conclusion of most legal scholars and commentators: the President cannot preemptively pardon himself before leaving office.

Then there is the problematic exercise of executive clemency to impede an investigation, a “corrupt intent” which Shugerman said could make the President “liable for obstruction of justice charges.”

Griffin noted that if Trump suddenly pardoned an associate like Flynn, who has acknowledged that he is cooperating with the special counsel, “he runs the risk of appearing to try to influence, intimidate or curry favor—or any of the above—with a witness, and that might constitute impeding, interference or obstruction.”

Mueller has assigned career government attorney Michael Dreeben to research the limits of executive clemency, according to Bloomberg.

POTUS has no influence over state charges

The most significant workaround for law enforcement is the President’s inability to pardon individuals found guilty of state crimes.

“That’s the linchpin of all of this,” Shugerman told TPM. “[Mueller’s strategy] seems to be to make sure the indictments he brings and the guilty pleas he obtains preserve for state prosecutors the backup plan against pardons.”

Information gleaned from proffer agreements or possible grand jury testimonies provided by cooperating witnesses like Flynn or former campaign aide George Papadopolous won’t be affected by executive pardons, noted Mark Osler, a a former federal prosecutor who now serves as a clemency expert at the University of St. Thomas Law School.

Parallel local probes are already underway in New York, where Attorney General Eric Schneiderman and Manhattan District Attorney Cy Vance are investigating indicted former Trump campaign chairman Paul Manafort’s financial and real estate dealings.

Analogue charges for federal crimes such as money laundering exist on the local level in every jurisdiction, Griffin noted. New York would be the likeliest legal battleground if Trump preemptively pardoned individuals like his son-in-law Jared Kushner or son Donald Trump Jr., since his campaign was run out of the Trump Organization’s Manhattan offices.

White House insists it’s not focused on pardons

According to Trump administration officials, pardons are the last thing on their mind.

After Trump in mid-December offered a vague “let’s see” to reporters asking if he planned to pardon Flynn, White House special counsel Ty Cobb played cleanup, saying “there is no consideration being given” to that matter.

“I think before we start discussing pardons for individuals we should see what happens in specific cases, too,” White House press secretary Sarah Huckabee Sanders said at a recent press briefing.

This delay is strategic, Griffin argued, adding that she believes the President will eventually make “very aggressive use” of his pardon power.

“I think it’s likely to come in the later stages of the Mueller investigation so as to preserve as many options as possible along the way,” she said.

Trump has already circumvented regular DOJ processes

There is plenty of precedent for President Trump acting unilaterally in a way that leaves his Justice Department scrambling. Previous administrations have carefully conferred with the Department of Justice’s Pardon Attorney, but in this as in so much else, Trump prefers to act alone and let the rest of the government mop up later.

Consider Trump’s harsh criticism of his own Attorney General Jeff Sessions a few months into his presidency, or the way he handled the pardon of Arizona Sheriff Joe Arpaio, whose flagrant misconduct was the butt of dark jokes for years before his conviction.

At first, Trump reportedly asked Sessions to abandon the case against Arpaio, which Sessions declined to do. The President then declared that Arpaio’s conviction, for disregarding a court order to stop patrols he’d ordered to track down undocumented immigrants, must be completely erased, even though Arpaio had bragged about disregarding the order. A legal wrangle has ensued.

If Trump cares enough about Flynn—or what Flynn might say—to force the Mueller probe to drop the case against him, the move might be unprecedented, but would not be out of line with the chaotic first year of his presidency. As far as Trump is concerned, the main risk of an unprecedented pardon would be to his popularity—his already-low approval ratings remain a festering sore spot.

Osler, the clemency expert, told TPM that the kind of “jump-the-line stuff” that occurred with Arpaio’s case “is highly unusual” and unfair to those who pursue standard petitions for executive clemency.

But Osler noted that Ford’s pardon of Nixon and Bill Clinton’s pardon of fugitive financier Mark Rich “happened at great cost to those presidents” and became a “negative part of their lasting legacy.”

Smears of DOJ and FBI help clear path for future pardons

Meanwhile, the administration and its GOP allies continue to seek weak spots in the DOJ investigation itself, sometimes with help from allies within the Justice Department, where deputy FBI director Andrew McCabe is said to be planning on an abrupt retirement as soon as he qualifies

Consider the Republican emphasis on the role of Peter Strzok, who was removed from the investigation for using his company phone to send uncensored text messages discussing his distaste for then-candidate Trump. Months after his removal, news of the texts broke through a private DOJ briefing to reporters, which the department said was not authorized by its press office.

Trump taunted McCabe on Twitter with hints of a firing before he qualifies for his full pension:

FBI Deputy Director Andrew McCabe is racing the clock to retire with full benefits. 90 days to go?!!! — Donald J. Trump (@realDonaldTrump) December 23, 2017

Then there is the emphasis from team Trump on the Steele Dossier (“the Dodgy Dossier,” as Carter Page and others insist on calling it), a raw intelligence report that is unlikely to prove more than incidental to any serious legal proceedings against the president or his allies. The dossier contains lots of quid but no quo; it was also commissioned by the Clinton campaign (which picked up the initial anti-Trump research contract at Steele’s employer, Fusion GPS, from right-wing billionaire Paul Singer’s mouthpiece, The Washington Free Beacon), a fact which remained a secret until late this year. As always, Trump and his allies both in office and in the conservative media world leapt at the opportunity to criticize Trump’s onetime electoral opponent, despite the conservative media world hiring Fusion in the first place.

If the Trump camp can discredit the probe, the president could make the act of firing people who could potentially prosecute him seem more reasonable.

This post has been updated.