On Friday, Sen. Charles Grassley (R-Iowa), the chair of the Senate Judiciary Committee, sent a seven-page, single-spaced letter posing 16 questions to Deputy Attorney General Rod Rosenstein.

Grassley’s letter asked Rosenstein to explain, in detail, the circumstances surrounding his appointment of Robert Mueller as special counsel, the parameters of that appointment, and the authority Rosenstein gave Mueller to, among other things, proceed before the secret Foreign Intelligence Surveillance Act court.

Here is what you need to know to understand this letter and the three big take-aways.

1. Rosenstein’s Special Counsel Appointment Letter Was a Ruse

Rosenstein’s May 1, 2017 special counsel appointment letter was a ruse, and the August 2, 2017 “clarification” was no such thing. On May 17, 2017, Rosenstein appointed former “FBI Director Robert S. Mueller III to serve as Special Counsel to oversee the previously-confirmed FBI investigation of Russian government efforts to influence the 2016 presidential election and related matters.” In the appointment letter, Rosenstein authorized Mueller to:

“conduct the investigation confirmed by then-FBI Director James Comey in testimony before the House Permanent Select Committee on Intelligence on March 20, 2017, including:

any links and/or coordination bet ween the Russian government and individuals associated with the campaign of President Donald Trump; and any matters that arose or may arise directly from the investigation; and any other matters within the scope of 28 C.F.R. § 600.4(a).”

However, in a four-page memorandum to Special Counsel Mueller on August 2, 2017, Rosenstein stated: “The May 17, 2017 order was worded categorically in order to permit its public release without confirming specific investigations involving specific individuals. This memorandum provides a more specific description of your authority. The following allegations were within the scope of the Investigation at the time of your appointment and are within the scope of the Order.”

At that point, the memorandum went black, redacting the first portion of the charge. Then, left unredacted were two sets of allegations against Paul Manafort, to be investigated: first, whether Manafort committed crimes by colluding with Russian government officials to interfere with the 2016 election, and second, whether he committed crimes related to payments he received from the Ukrainian government. Then the next several paragraphs are redacted, before concluding “[y]ou therefore have authority to continue and complete the investigation of those matters, and additional matters described in 28 C.F.R. § 600.4(a).”

This strange sequencing, coupled with the redaction, garnered much of Grassley’s focus. Grassley directed Rosenstein to provide the Judiciary Committee “an unredacted copy of the August Memorandum and any other documents delineating, describing, or supporting the jurisdiction and authority of the special counsel.”

In doing so, Grassley stressed that he is not the only one to express concern about the propriety of this procedure and the extensive redactions in the memorandum. Rather, Grassley noted “it is no surprise” that federal judge T.S. Ellis—the presiding judge in the special counsel’s criminal case against Manafort—“expressed some skepticism about a heavily redacted August 2017 memorandum that was drafted three months after you issued the Order appointing Robert Mueller as Special Counsel, and that you both now assert details the actual scope of his investigation.”

Grassley added that Ellis had ordered the special counsel to provide an unredacted copy of the August memorandum to the court, which Mueller’s team did last Thursday. Grassley concluded: “Like the Judiciary, Congress is a separate branch of government with its own constitutional duties that often require access to Executive Branch information.”

Grassley went further, noting “[t]he 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. 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 then asked Rosenstein to explain why the August 2, 2017 memorandum was not drafted until that late date.

The judiciary chair continued: “The Department’s decision to withhold a precise description of the scope of the special counsel investigation, obscures how the Department is spending significant amounts of taxpayer dollars and leaves murky the actual jurisdictional limits on Mr. Mueller’s authority as well as how those limits are determined.”

Then Grassley went for the jugular, writing: “More troubling, the Department’s close hold of this information arises amidst multiple instances of the Department’s resistance to transparency on the purported grounds of national security, even when the information sought to be restricted did not pose any legitimate security risk, or was already public.”

One might add: Or when Department of Justice staff leaks extensive details to the press that unmask top-secret informants.

2. Rosenstein Ignored Department of Justice Regulations

In appointing a special prosecutor, Rosenstein ignored Department of Justice regulations. The second clear focus of Grassley’s letter concerned DOJ regulations governing special counsel appointments and Rosenstein’s apparent disregard for those provisions.

As backdrop, it is important to understand that while Congress has defined the attorney general and DOJ’s authority through a series of statutes, the provisions governing special counsel appointments (and functioning), come instead from regulations promulgated by the DOJ, specifically 28 U.S.C. § 600.1-600.15.

Grassley walks through these provisions, highlighting inconsistencies between the regulatory mandates and Rosenstein’s appointment. For instance, he stresses that “section 600.1 states the Attorney General ‘will appoint a Special Counsel when he or she determines that criminal investigation of a person or matter is warranted,’” before adding that the “regulations do not authorize counterintelligence investigation” (emphasis in original).

Yet, as Grassley points out, the appointment order authorizes the special counsel to complete the investigation discussed by then-FBI Director James B. Comey in his testimony before Congress. That testimony expressly referred to the investigation as a “counterintelligence investigation.” Does the special counsel have the authority to conduct a counterintelligence investigation? If so, what is the source of that authority? Grassley asks.

Does the special counsel have the authority to conduct a counterintelligence investigation?

Next, Grassley notes that section 600.2(b) directs the attorney general to conduct “an initial investigation, consisting of such factual inquiry or legal research,” as necessary “to better inform the decision” of whether to appoint a special counsel. Did you do so, Grassley queries Rosenstein, asking him to also explain whether he considered whether it was possible to instead “mitigate any conflicts of interest [through] recusal of particular officials.”

Section 600.3(b) of the regulations also required the attorney general “to ensure an appropriate method of appointment” and “to ensure . . . a detailed review of ethics and conflicts of interest issues.” Did you do so and what were the results of this inquiry? Grassley asks.

This line of questioning seems particularly apropos given disgraced Trump-hater Peter Strzok’s initial involvement in the special counsel’s probe, and the continued involvement of Andrew Weissmann, a long-time DOJ attorney who cheered on the insubordination his former boss, Sally Yates, directed toward Donald Trump before the president fired her.

While seemingly tedious, these questions, and Grassley’s focus on the DOJ regulations, is not for naught. Rather, Grassley has zeroed in on the special counsel’s apparent disregard for the government regulations and, relatedly, the absurd argument Mueller’s team is advancing before Judge Ellis. In that case, Mueller’s team is arguing that even if Rosenstein did not comply with the mandates of the special counsel regulations, Manafort (and others) have no right to relief. What Grassley wants to know now is whether that is true and whether Rosenstein ignored the clear regulatory mandates.

3. Yes, This Is the Business of the Senate Judiciary Committee

Grassley makes one final key point: Yes, this is the Senate Judiciary Committee’s business. In directing Rosenstein to provide the Senate Judiciary Committee a copy of the unredacted August 2, 2017 memorandum and respond to the 16 questions, Grassley stressed Congress’ interests involved both legislative and oversight responsibilities.

In discussing the oversight responsibilities, Grassley’s letter turned terse, likely spurred by Rosenstein’s recent public comments casting congressional oversight of the Russian investigation as “extortion.” During a question and answer session, Rosenstein noted that the department’s independence does not prevent it from sharing priorities with the rest of the executive branch, “including the White House,” but portrayed congressional oversight as interference with department investigations.

Beyond the oversight responsibility, Grassley stressed the need for this information to allow Congress to respond legislatively.

Grassley returned fire, writing “despite much pontification to the contrary, it is not true that the Department always withholds information about ongoing investigations or other proceedings from Congress, particularly its oversight committees—nor should it.” The Iowa senator then reminded Rosenstein that “[i]n this very matter, Director Comey appropriately briefed Ranking Member Feinstein and me in March 2017 on the details of both the counterintelligence and criminal aspects of the various related probes as of that time.”

The Judiciary Committee chair took the opportunity to further remind Rosenstein that the “Committee has well established authority pursuant to the Constitution and the Rules of the U.S. Senate to oversee the Department’s activities, including its grant of authority to special counsels.” Here, Grassley wanted to know whether Rosenstein delegated to Mueller the attorney general’s authority to seek a secret surveillance order from the Foreign Intelligence Security Act court. Sen. Susan Collins had asked this question during an all-senators briefing on May 18, 2017, but as of yet, has not received an answer.

Beyond the oversight responsibility, Grassley stressed the need for this information to allow Congress to respond legislatively. Specifically, Grassley noted that “[o]n April 26, 2018, the Senate Judiciary Committee reported a bill to the full Senate that would codify current Department of Justice regulations regarding the appointment, authority, and supervision of a special counsel.”

The proposed law would also require the special counsel to provide reports to Congress. In other words, Congress is in the process of adopting the DOJ’s regulations that Rosenstein appears to have ignored without consequence, making those provisions thereby enforceable.

“[A]s we consider legislative proposals based largely on the Department’s current rules,” Grassley wrote, “it is vital that Congress has a clear understanding of how the Department is interpreting them.” The public would be well-served to understand these facts too.

A response is due by May 31, 2018.