In this weekly column "Cross-Exam," Elie Honig, a CNN legal analyst and former federal and state prosecutor, gives his take on the latest legal news. Post your questions below. The views expressed in this commentary are his own. View more opinion on CNN. Watch Honig answer reader questions on "CNN Newsroom with Ana Cabrera" at 5:40 p.m. ET Sundays.

(CNN) President Donald Trump and his supporters are in the exploratory phase of the impeachment defense game, trying various excuses on for size and hoping one resonates enough to get him through the mushrooming Ukraine scandal.

Earlier this month, Trump tweeted that "As the President of the United States, I have an absolute right, perhaps even a duty, to investigate, or have investigated, CORRUPTION, and that would include asking, or suggesting, other Countries to help us out!" Some Trump supporters, including Sen. Lindsey Graham and Rudy Giuliani, concur with the notion of an armor-clad Trump riding into Ukraine to set straight their crooked politicians.

Theoretically, Trump is correct that a president has broad power to combat foreign corruption, particularly in countries that receive hundreds of millions of dollars in foreign aid from the United States. The problem is that it's an absolute fiction to suggest this is what President Trump was doing with Ukraine.

Indeed, the evidence at the heart of the Ukraine scandal makes clear that Trump had a laser focus not on rooting out Ukrainian corruption generally, but solely on generating dirt on his political opponents. In a July 25 phone call , Trump repeatedly exhorted Ukrainian President Volodymyr Zelensky to investigate Joe and Hunter Biden, with nary a mention of any other case or investigation. And a series of texts among State Department officials and Giuliani establish that the participants understood there was only one "deliverable" (as Ambassador to the European Union Gordon Sondland put it): an investigation of the Bidens or at least an announcement of one. (Trump has denied that taking down Biden was his main purpose, and has said that he is merely seeking to root out corruption.)

When Trump was asked recently to name a single foreign corruption case he had shown any interest in -- besides those involving his political opponents -- Trump spun in a circle: " You know, we would have to look. .." Apparently, Trump is still looking.

If the US government -- typically through the Justice Department -- wants to address foreign corruption lawfully and through official channels, it can formally request cooperation through a Mutual Legal Assistance Treaty . Such requests are commonplace -- I submitted them even as a line-level, in-the-trenches federal prosecutor -- and the fact that Trump operated outside established legal channels says something about his intent.

As a prosecutor, I've seen all manner of defenses. Some have been compelling, others vaguely plausible, still others laughable. But the notion of Donald J. Trump as the next corruption-buster in the mold of Preet Bharara Pat Fitzgerald or Sally Yates would be comedic if it wasn't so hypocritical and misleading. Trump may yet come up with a compelling defense against the rising tide of impeachment, but this sure isn't it.

Now, your questions:

Paul (Massachusetts): What happens next in the courts on Congress' effort to obtain Trump's tax returns?

The House won a major victory when a federal court of appeals in Washington, D.C. ruled by a 2-1 vote that its subpoena to Trump's accounting firm Mazars USA is "valid and enforceable." The opinion held that Congress has broad -- though not unlimited -- power to subpoena evidence. Trump's legal team now is "reviewing the opinion and evaluating all appellate options."

Trump has two cards left to play. First, he can seek re-argument before the DC Court of Appeals sitting " en banc " -- meaning the entire membership of the court of appeals hears the case, rather than the typical three-judge panel. En banc review is granted only in rare circumstances.

Second, he can seek "certiorari" -- review -- in the United States Supreme Court. The Supreme Court is very selective about which cases it takes, typically accepting well under 5% of all cases seeking certiorari. If the Supreme Court declines to hear the case, then it's over, and Congress gets the tax returns. If the Supreme Court does decide to take the case, then it will have the final word.

Monica (Canada): Could other people involved in the Ukraine scandal, like Rudy Giuliani, face criminal charges or repercussions, regardless of whether Trump is impeached?

Yes, people other than the President certainly could be charged criminally for their roles in the Ukraine scandal, even if that evidence comes to light through an impeachment investigation. While Congress itself cannot charge somebody with a crime, it can refer a case for investigation and potential prosecution to the Justice Department. The Justice Department would then need to make its own determination about whether criminal charges are warranted.

Alex: Did Rudy Giuliani break the law by giving the impression that as a private citizen, he could make a deal on behalf of the President and the United States?

An obscure federal law called the Logan Act makes it a crime for a private person to attempt to conduct foreign policy on behalf of the United States. While Giuliani's conduct arguably meets the legal definition of the crime, it is exceedingly unlikely he will be prosecuted under that law.

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The Logan Act is broad and vague. The government likely has the authority to empower a private citizen to deal with a foreign country but it is unclear who in government can give such permission; for example, Giuliani might argue that Trump, as president, duly empowered him to conduct foreign relations with Ukraine. Partly because the Logan Act lacks clarity, it has never actually been used to send a person to prison in its 200-year history. It seems unlikely that Giuliani would become the first.

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Three questions to watch:

1. Will more career public servants (like Fiona Hill and Marie Yovanovitch ) come forward with testimony about the shadow Ukrainian foreign diplomacy effort led by Giuliani?

2. What will Gordon Sondland 's congressional testimony reveal about whether Trump genuinely intended to pose a "quid pro quo" to Ukraine?

3. Will the administration comply with or defy congressional subpoenas on the White House, Vice President Pence, and other top officials?