A prosecutor was investigating Trump's claim that the FBI did not properly look into Hillary Clinton's role in a uranium deal while she was secretary of state.
The case relates to media disclosures about the Clinton Foundation during the 2016 election.
The Supreme Court justice underwent treatment for pancreatic cancer last month.
The former president released a statement claiming he hasn't spoken to the accused sex trafficker in over a decade.
It seemed to "be the responsible thing to do" said Bernie's wife, Jane Sanders.
Michael Bromwich is also representing booted former FBI deputy director Andrew McCabe.
Andrew McCabe, the former acting FBI director whom Trump has pilloried, apparently okayed the disclosure of information that hurt the Clinton campaign.
A spokesman for Hillary Clinton called the probe "a sham."
An FBI investigation into Hillary Clinton's ties to the deal has found no wrongdoing.