Special counsel Robert Mueller's recent admission that the May 17, 2017, Justice Department order defining the scope of his investigation was just for show, and that the real extent of his probe is a secret, is reverberating on Capitol Hill.

On Thursday, Senate Judiciary Committee chairman Chuck Grassley wrote to deputy attorney general Rod Rosenstein, asking to see the document outlining the true scope of the Mueller investigation. Grassley noted that earlier this month, federal judge T.S. Ellis " expressed some skepticism" about the secrecy of Mueller's authority and demanded to be shown an Aug. 2, 2017, memo that is said to define the probe in detail. Now Grassley wants to see it, too.

In court before Ellis, Mueller lawyer Michael Dreeben revealed that the May 17 appointment order is not a "factual statement" of Mueller's assignment. "The regulations nowhere say that a specific factual statement needs to be provided publicly," Dreeben added. "The specific factual statement … was conveyed to the special counsel upon his appointment in ongoing discussions [between Rosenstein and Mueller] that defined the parameters of the investigation."

Dreeben explained that those discussions between Rosenstein and Mueller, incorporated in the Aug. 2 memo, established that Mueller had the authority to investigate Paul Manafort's financial dealings that Manafort contends are beyond the scope of Mueller's investigation into allegations of Trump-Russia collusion in the 2016 election.

"The Aug. 2 memorandum confirms the acting attorney general's understanding both at the time of our appointment and as of the time of that memo that these crimes are within the scope of our authority," Dreeben told Ellis. "And the explanation for the greater detail in the Aug. 2 memo is that the public order was not the place or occasion to provide details about the matters that the special counsel was to investigate."

In another court, Mueller released the Aug. 2 memo, but it was so heavily redacted that it revealed little beyond two brief paragraphs on the Manafort case.

Ellis ordered the Mueller office to produce an unredacted copy of the Aug. 2 memo. The office complied, although the memo remains under seal and is no more available to the public than it was before.

Now Grassley argues that the Senate has a right to see the memo, too. "This committee likewise should be permitted to review the true nature and scope of the special counsel's investigation," Grassley wrote to Rosenstein. "It is unclear precisely how, or whether, the Department is following its own regulations, what the actual bounds of Mr. Mueller's authority are, and how those bounds have been established."

In the letter, Grassley appeared unhappy that he, as the chairman of the Senate committee charged with overseeing the Justice Department, did not learn the true extent of the Mueller investigation until long after Mueller was appointed.

"The public, as well as Congress, only learned a fraction of the investigation's actual scope in April 2018 — nearly a year after Mr. Mueller’s appointment — when he filed a heavily redacted copy of the August memorandum in federal court," Grassley wrote. "From the small snippet we can see, the difference in the number and the nature of the details described in the Appointment Order and three months later in the August memorandum is significant. Even if there may be legitimate reasons to limit the public release of that information for a time, those reasons would not justify withholding the scope information from congressional oversight committees."

Grassley also noted that the Justice Department's secrecy with the Mueller appointment comes after months in which the department withheld a variety of other documents related to the Trump-Russia affair.

Finally, Grassley added that in the independent counsel investigation of Bill Clinton in the 1990s, "the scope and changes made to [the Ken Starr investigation] were transparent." For example, when Starr sought to expand his probe to include the Monica Lewinsky matter, he had to ask a three-judge panel for permission, and when that permission was granted, the order was released to the public, in full, within two weeks.

Mueller's investigation is not like that. But changes could be on the way. Grassley made some in his party unhappy when he joined Democrats in supporting a bill, which has not received a vote in the Senate, to protect the office of special counsel. But the bill, Grassley reminded Rosenstein, would demand more transparency from a special counsel. "The legislation also would require additional reports to Congress about significant steps taken and conclusions reached in a special counsel investigation," Grassley wrote. "The draft legislation thus aims to ensure the independence and transparency of a special counsel's work — any special counsel's work."