However, many legal experts say Giuliani needn’t be quaking in his boots — at least on that score.

While the Justice Department has embarked on an effort to crack down on violations of the Foreign Agents Registration Act, two recent high-profile attempts by prosecutors to advance that drive met with failure.

Early last month, a federal court jury in Washington took only four hours to acquit former Obama White House counsel Greg Craig on a charge of scheming to deceive the Justice Department’s foreign-agent registration unit about his work for Ukraine.

A few weeks later, a judge in Alexandria dealt another blow to the FARA enforcement campaign by tossing out the prosecution of Bijan Rafiekian, a Trump transition adviser and ex-business partner of former national security adviser Michael Flynn. The judge said the evidence in the case, involving lobbying for Turkish interests, was insufficient to sustain a pair of guilty verdicts a jury returned in July.

As prosecutors mull whether to proceed against Giuliani, who has thus far not been charged with any crime, those well-publicized setbacks could prompt reluctance to press forward with a FARA-focused case without overwhelming evidence of guilt.

“In the wake of the outcomes in the Greg Craig and Rafiekian cases, the department might engage in additional pressure testing of the evidence in support of a potential FARA charge to maximize the likelihood of a conviction,” said David Laufman, a former federal prosecutor who stepped down last year as head of the Justice Department section responsible for FARA enforcement.

The public defense Giuliani has offered is uncannily similar to those offered by Craig and Rafiekian. Both of those men acknowledged receiving large sums of money from abroad, but disputed the Justice Department’s claims about whom the men were representing.

While Craig and his law firm collected more than $5 million from an oligarch supporting Ukraine’s government, the veteran D.C. lawyer maintained that his interactions with several journalists — exchanges central to the case against him — were not in service of his Ukrainian clients but to protect his own reputation and that of his law firm at the time, Skadden Arps.

In Rafiekian’s case, prosecutors alleged that the lobbying and PR activities he and Flynn undertook were part of a Turkish government campaign to get the U.S. to expel a dissident Turkish cleric who has lived in self-imposed exile in the U.S. for decades. Rafiekian’s lawyers claimed their client was simply working for an ordinary business, a Dutch company with interest in improving the investment climate between the U.S. and Turkey.

Giuliani is taking a similar tack. He’s owned up to contacts with U.S. officials about ousting the American ambassador to Ukraine and acknowledged campaigning to pressure Ukrainian officials to reopen investigations that could be damaging to Joe Biden, the former vice president and current Democratic presidential candidate.

However, Giuliani maintains those entreaties were not made at the behest of his paying clients with Ukrainian ties, including the two men who were indicted and arrested earlier this month on campaign finance charges, Lev Parnas and Igor Fruman.

The former New York mayor says his lobbying about the U.S. ambassador and to prod Ukraine’s government to focus on Biden was for another, far more famous client he was representing, albeit without pay: President Donald Trump.

Giuliani has been viewed as in jeopardy on FARA because of language in the Parnas and Fruman indictment that says the charged men were acting to “advance … the political interests of at least one Ukrainian government official with whom they were working.” The indictment also specifically alleges that “Parnas’s efforts to remove the Ambassador were conducted, at least in part, at the request of one or more Ukrainian officials.”

Prosecutors say Parnas and Fruman committed to raise at least $20,000 last year for “a sitting congressman” — apparently Rep. Pete Sessions (R-Texas) — as they sought to enlist the lawmaker in efforts to oust the ambassador, career diplomat Marie Yovanovitch. Sessions wrote to Secretary of State Mike Pompeo, urging her dismissal. She was recalled early from her post in May of this year.

Laufman said wording in the indictment about plotting to remove the ambassador on behalf of Ukrainian officials seems to go to the heart of FARA. “That sentence to me, on its face, indicates that comes within the scope of the statute,” he said. “That language in the indictment raises serious questions if Giuliani knew of this alleged conduct by these two characters.”

Still, while the indictment alleges a variety of campaign finance laws were broken, including using straw donors and violating the ban on donations from foreigners, there is no FARA charge against any of the defendants, let alone Giuliani.

That could be because a criminal FARA charge requires showing a defendant broke the law “willfully,” meaning he or she knew about the statute — at least in general terms — and intentionally sought to defy it. A good-faith belief that one was not required to register is a defense.

“The government must provide sufficient evidence to prove beyond a reasonable doubt that a defendant knew about the requirement to register and failed to do so,” Laufman said.

That can be a heavy burden in the absence of clear documentary proof that a defendant chose to break the law. There’s also the question of whether prosecutors can prove whether someone was acting at the “direction or control” OF [for] a foreign national, government or political party.

“You can home in on a number of different definitional aspects in a FARA case and say, ‘I didn’t need to file,’” said D.C. lawyer Robert Driscoll. “To prove the violation is willful is really hard to do because half the attorneys in town can’t give you decent FARA advice. ... You’d have to be really dumb to show enough criminal intent to willfully violate FARA.”

Under Justice Department policy, prosecutors typically have to be convinced that it is more likely than not that a defendant will be convicted on a particular charge before filing it as part of a criminal case.

Another complexity is that while many Trump critics seem to be itching for a Giuliani indictment, charging him with a FARA violation could undercut the notion that he was working for Trump in any dealings related to Ukraine. The plausibility of that argument makes it harder to prosecute Giuiliani criminally, but could make it easier to use Giuliani’s acts against Trump in the ongoing impeachment probe.

Giuliani did not respond to repeated requests for comment for this article.

The indictments against Craig and Rafiekian were widely seen as part of a crackdown on unregistered foreign agents in the U.S., driven in part by the controversy over Russian interference in the 2016 presidential race and in part by perceptions that the Justice Department’s efforts to enforce FARA had been too meek.

A Justice Department Inspector General report released jn 2016 found only seven criminal FARA cases brought by federal prosecutors during the preceding half century. Only one of those cases resulted in a contested trial. Four of the cases led to guilty pleas, although not always to FARA. Two cases were dismissed.

The Justice Department’s official response to the watchdog report called criminal FARA cases “challenging” and cited the “high burden” prosecutors have to meet to get a conviction.

The lax enforcement in recent decades gave many Americans who deal with lobbying and PR work in the U.S. for overseas clients the impression that compliance was essentially on an honor system. It also led to calls from Congress to toughen the statute, although the legislative effort seems to have stalled.

Technically, neither Craig nor Rafiekian was charged directly with failing to register under FARA.

Although the indictment against Craig accused him of illegally evading registration, he was charged only with making false statements in a FARA submission and with a scheme to mislead Justice’s FARA unit. A judge threw out the first charge, while a jury acquitted him on the second.

Rafiekian was accused of conspiring to make false statements in a FARA filing and of violating a related law barring actions for a foreign government in the U.S. without notifying the attorney general. A jury convicted him on both counts, but a judge overturned those verdicts and dismissed the case. On Wednesday, prosecutors filed a notice appealing that ruling, but it does not appear the Justice Department has yet made a final decision about whether to challenge the decision.

To be sure, the government has filed other criminal FARA cases in recent years, most notably the prosecution of former Trump campaign chairman Paul Manafort and deputy Rick Gates for their Ukraine-related work. However, the government was never required to prove the FARA charges in court because the men pleaded guilty.

The cases also involved allegations of a vast scheme of criminal activity, including massive tax evasion, money laundering and failing to report foreign bank accounts. Manafort and Gates appear have been willing to admit to the FARA offenses in order to try to resolve the much wide-ranging charges against them.

Prosecutors included FARA charges in a case filed this week against California businessman Imaad Zuberi, but the charges also included allegations of tax evasion and that he made more than 75 campaign donations on behalf of foreign nationals and often under false names. Prosecutors also appear unlikely to have to prove the FARA charges, as Zuberi has agreed to plead guilty as part of a plea deal.

But several other potential FARA cases have been turned down in recent months, particularly by federal prosecutors in the same Manhattan U.S. Attorney’s Office which obtained the indictment of Giuliani’s allies and is reportedly looking into his conduct.

Craig’s defense attorneys say that before he was charged, federal prosecutors in New York were considering a failing-to-register FARA charge against him. Plans for that were apparently dropped and authority over the case was moved to Washington.

During Craig’s trial in D.C., prosecutors from the Southern District sat in on some of the testimony as they considered whether to charge anyone else in connection with a FARA violation or other offenses in the effort to burnish Ukraine’s image in the U.S.

Despite testimony from Gates that he told top lobbyists Vin Weber and Tony Podesta they would be working for the Ukrainian government, soon after the trial wrapped up, prosecutors informed the men they would not face charges despite the fact they did not register until long after the lobbying project concluded. The firm Weber worked for until August, Mercury, also escaped prosecution. Podesta’s eponymous Podesta Group shut down in 2017, largely due to negative attention from the Manafort-linked work.

Weber, Podesta and the firms all denied wrongdoing.

Parnas and Fruman pleaded not guilty Wednesday during a court hearing in New York. Many lawyers say they could seek leniency by detailing what Giuliani knew about their backers’ abroad. “If they choose to cooperate, they could have inculpatory information as to Mr. Giuliani with respect to FARA,” Laufman said.

The former Justice Department official noted that even if prosecutors choose not to charge Giuliani with a crime, the law enforcement agency has other options: it could send the former mayor a letter urging him to register and could even file suit against him to demand that he do so. Last year, in the first such enforcement action in 28 years, Justice sued a Florida company that contracts to rebroadcast programs by Russia’s English-language media outlet, RT. A judge ordered the company to register under FARA.

In March, the Justice Department announced another step in its drive to reinvigorate FARA: naming Brandon Van Grack, a prosecutor from former special counsel Robert Mueller’s probe, to oversee enforcement of the foreign-agent law.

At a legal conference last month, Van Grack was asked whether prosecutors’ stumbles in the Craig and Rafiekian cases would impact how the Justice Department would handle FARA cases in the future.

Van Grack suggested that, despite the setbacks in those prosecutions, they had sent the message that the Justice Department is serious about enforcing FARA.

“FARA enforcement remains a top priority,” he declared. He went on to ask the assembled FARA lawyers “whether the advice you would give a registrant today is any different than it was the day before?”

“I suspect the answer is no,” he added.

Theodoric Meyer contributed to this report.