The Department of Justice is refusing to release details of the process that led to FBI Director Robert Mueller being granted an ethics waiver to be able to serve as special counsel investigating Trump’s campaign involvement with Russia during the 2016 election.

On Friday, the agency released a one-sentence memo that confirmed Mueller was granted a conflict-of-interest waiver to serve in the position.

The waiver is believed to be related to Mueller’s previous work as a partner at WilmerHale law firm, which is also the firm that represented former Trump campaign chairman Paul Manafort and White House adviser Jared Kushner.  However, documents signed by the Justice’s top career official, Associate Deputy Attorney General Scott School, provide no evidence as to the grounds for the waiver.  It’s actually so vague that it doesn’t even state why Mueller would need the release.

“‘Pursuant to 5 CFR 2635.502(d), I hereby authorize Robert Mueller’s participation in the investigation into Russia’s role in the presidential campaign of 2016 and all matters arising from the investigation,’ Schools wrote in the ‘authorization’ signed on May 18, one day after Deputy Attorney General Rod Rosenstein formally appointed Mueller to the position.”

The Justice Management Division of the agency found a two-page “recommendation memorandum” per POLITICO’s request, but declined releasing it because it would interfere with the “deliberative process inside the department.”

The secrecy revolving the situation could result in some Republican lawmakers and Trump allies to raise doubts about the impartiality of the Mueller investigation.  Experts are troubled that the Justice Department hasn’t been more open about the information of Mueller’s waiver.

“‘I think it’s sloppy,’ said Richard Painter, a former White House ethics lawyer under President George W. Bush. ‘The conspiratorial side of me thinks somebody at Justice is not giving you the explanation for the waiver because they want to create the impression that Robert Mueller has a problem when Robert Mueller doesn’t have a problem. … This is going to lead to Fox News conspiracy talk.'”

However, the Department of Justice has been more open about details of waivers to other officials.  In May, a bath of ethics waivers granted to Noel Francisco were released in response to a lawsuit filed by a liberal watchdog group American Oversight.  Other waivers the agency has released also seem to be consistent of a recommendation and approval.

The Justice Department is defending the issue by saying that it is protected by “deliberative process privilege.”

“‘The memo is protected by the deliberative process privilege (Exemption 5 of the Freedom of Information Act). This is in contrast to the communications related to the Francisco waiver, in which the deliberative discussions were expressly adopted by the decision maker,’ the official said.”

A statement was made a week after Mueller’s appointment in May by Sarah Isgur Flores, the Justice Department spokeswoman.  However, her statement was vague.

“‘Government ethics regulations permit the Department of Justice to authorize an employee to participate in a matter where their former employer represents a party,’ Flores said on May 23. ‘While we cannot confirm or deny the applicability of the regulation to the matters to which Special Counsel Mueller was appointed, we can confirm that the Department ethics experts have reviewed the matters and determined that Mr. Mueller’s participation in the matters assigned to him is appropriate.'”

While Mueller worked at the firm, he had no involvement with cases regarding Manafort or Kushner.