EXPLAINER: What to know about the Giuliani investigation

NEW YORK (AP) — The long-running federal investigation into Rudy Giuliani's dealings in Ukraine moved back into public view Wednesday when federal agents seized electronic devices from the former mayor's home and office.

The search was the latest development in an inquiry that overlapped with the first impeachment trial of Donald Trump, who was accused of pressuring the leaders of Ukraine to investigate Joe Biden and his son.

The probe involves a complex web of international characters who dealt with Giuliani as he tried to stir up support for a Ukrainian investigation of the Bidens.

Federal prosecutors haven't disclosed which elements of Giuliani's work are the focus of their probe, currently being led by Audrey Strauss, the U.S. attorney for the Southern District of New York.

But at least one part is an examination of whether Giuliani failed to disclose to the U.S. government work he did on behalf of foreign entities.

WHY IS GIULIANI UNDER INVESTIGATION?

Giuliani’s lawyer, Robert Costello, said the search warrants involved an allegation that Giuliani failed to register as a foreign agent.

The Foreign Agents Registration Act, originally passed before World War II to expose Nazi propaganda, requires people to disclose to the Justice Department when they have been hired to lobby in the U.S. on behalf of foreign governments, figures or political entities.

Criminal prosecutions under the law were once rare, but there have been a number of high-profile cases in recent years, including during special counsel Robert Mueller's investigation into Russian election interference. Trump's campaign chairman, Paul Manafort, was convicted of failing to register work he'd done for a political party in Ukraine. Trump's first national security adviser, Michael Flynn, admitted making false statements about work he'd...