"I have been sitting here looking in the federal code trying to find collusion as a crime", Giuliani said in an interview on Fox News Channel's "Fox & Friends".
She noted, in addition, that "collusion" with the Russians could be a type of criminal conspiracy - which certainly is a crime.
Mueller has even suggested recently that the President's tweets will be examined for evidence of obstruction.
"I don't know", Giuliani said before pivoting to other subjects.
The former NY mayor said if Trump is interviewed by Mueller's legal team, "Our real concern is they're going to set up a perjury trap", attempting to catch Trump, who often misstates facts, in a lie, which is a criminal offense.
Mueller might decide, for example, that a crime was committed if he finds evidence that an American was involved in the hack of Democrats, either by soliciting it or paying someone to do it.
While Special Counsel Robert Mueller is tasked with uncovering alleged collusion between the Trump campaign and Russian Federation in the runup to the 2016 election, Manafort is being tried on unrelated tax and bank fraud charges dating back over a decade. "He didn't pay for the hacking".
Mueller is expected to adhere to U.S. Justice Department guidelines to not indict a current president, but is expected to write a report on his findings that could, if wrongdoing is alleged, be turned over to Congress.
That came after a confusing Monday morning media tour by Giuliani, during which he first floated his collusion as legal theory.
Rudy Giuliani launched a fresh defense of the US President on Monday. The strategy may be the latest in Trump's efforts to strip legitimacy from the Mueller probe, which he has long denounced as a "witch hunt".
Rudy Giuliani is purposely exchanging "Conspiracy" for "Collusion" to intertwine a legal term of art with a political one.