You won't go far wrong with my post below, but the reality is much more complicated. For example, I say that OIG doesn't have "subpoena power," which is only true concerning grand jury subpoenas. They do have administrative subpoena power (and I should have known that, because for a few years I worked in a program where we used administrative subpoenas). However, OIG's jurisdiction is limited to personnel of components of DoJ (as well as contractors and grantees). Therefore, their administrative subpoenas are limited in that regard. It can get complicated, but here's what Vox says about OIG, and this works for our purposes. Please note that while Vox speaks as if they're describing all IGs, they're really describing only the DoJ situation--each IG has to be viewed on its own:
A department’s IG has the authority to examine relevant records from the department, from memos to emails. IGs have [administrative] subpoena power and can arrange interviews of current employees — interviews in which it would be a crime to make false statements. So their investigations have the potential to be quite vigorous.
Yet one crucial thing to understand is that inspectors general have no authority to actually charge anyone with crimes (or indeed, to impose any disciplinary actions). Their investigations end when they assemble reports on what they found. These reports, which are generally made public, can recommend that people be prosecuted, but actual charging decisions are left to elsewhere in the Justice Department.
And from The Atlantic:
“Horowitz is an extremely experienced and capable lawyer and former prosecutor,” said David Kris, a founder of Culper Partners who served as the assistant attorney general for the DOJ’s National Security Division from 2009 to 2011.
Horowitz’s power is fairly limited—in a noncriminal review such as the one Horowitz has been conducting into the FBI’s conduct, the inspector general’s office cannot compel testimony from former or non-DOJ employees, for example.* “While current employees have to cooperate with the investigation or face discipline, employees who have left DOJ can refuse to talk, as can everyone else who does not work for DOJ. That makes this kind of review far less authoritative than a criminal investigation,” said William Yeomans, a former deputy assistant attorney general who spent 26 years at the DOJ. “The standards for including something in an IG report are lower than that for proving a fact in a criminal case. I also know from personal experience that the IG gets facts wrong sometimes.”
I don't want to venture further into this for now, because it gets murky--for example, there are jurisdictional disputes between OIG and OPR (Office of Professional Responsibility). But hopefully this gives a general idea of what we're looking at with OIG. John Durham is the main actor here.
We're at a bit of a slow point regarding actual news about the investigation into the Russia Hoax--although I expect developments in the not too distant future. In the meantime, spurred by a request from commenter Joe, this may be a good time to offer a bit of information about an entity within the Department of Justice that has been repeatedly mentioned but concerning which there are misconceptions: the Office of the Inspector General, or, OIG.
First of all, as the name ("Inspector") suggests, OIG is not a strictly investigative body in the sense that the Federal Bureau of Investigation is. OIG has a handy About The Office web page that explains the idea behind its creation and operation. Before we get to that, however, we need to be clear that there are actually many other OIGs. Some of those--such as the OIG for the Intelligence Community or for the Department of State--are potentially of great interest in the Russia Hoax, although to this point most attention has focused on OIG-DoJ. Here's how Wikipedia explains the general concept of an OIG:
In the United States, Office of Inspector General (OIG) is a generic term for the oversight division of a federal or state agency aimed at preventing inefficient or unlawful operations within their parent agency. Such offices are attached to many federal executive departments, independent federal agencies, as well as state and local governments. Each office includes an inspector general (or I.G.) and employees charged with identifying, auditing, and investigating fraud, waste, abuse, embezzlement and mismanagement of any kind within the executive department.
In the United States, other than the military departments, the first Office of Inspector General (OIG) was established by act of Congress in 1976 under the Department of Health and Human Services, to fight waste, fraud and abuse in Medicare, Medicaid, and more than 100 other HHS programs. ...
There are 73 federal offices of inspectors general, a significant increase since the statutory creation of the initial 12 offices by the Inspector General Act of 1978.
Although the basic idea of an OIG is to focus on "fraud, waste, abuse, embezzlement and mismanagement of any kind", not all OIGs operate in the same way. The basic concept, however, is always the same: the OIG is always focused on internal operations of an executive agency. Here we deal only with DoJ's OIG and from this point on references to "OIG" refer only to that entity.
OIG describes its nature and duties very much in the same fashion as Wikipedia:
The Office of the Inspector General (OIG) in the U.S. Department of Justice (DOJ) is a statutorily created independent entity whose mission is to detect and deter waste, fraud, abuse, and misconduct in DOJ programs and personnel, and to promote economy and efficiency in those programs. The OIG investigates alleged violations of criminal and civil laws by DOJ employees and also audits and inspects DOJ programs. The Inspector General, who is appointed by the President subject to Senate confirmation, reports to the Attorney General and Congress.
The Office of the Inspector General (OIG) consists of a front office, which is comprised of the Inspector General, the Deputy Inspector General, the Office of the General Counsel, and six major components. Each division is headed by an Assistant Inspector General.
So, we see that OIG is focused on internal operations and that its primary focus is promoting economy and efficiency. (I know--who knew the Federal Governement cared? We'll just skip over that.) The important thing to be aware of in this is that OIG has no prosecutorial powers. It can audit, it can inspect, and it can investigate, but it can only refer to DoJ for a prosecutive opinion. Further, since OIG operates on its own, rather than as an investigative arm of DoJ in a general sense (that would be the FBI), OIG has no access to a Grand Jury, which means that it cannot administratively subpoena documents from outside entities (banks, telecom companies, etc.) that aren't connected to DoJ (such as contractors). Its focus is always on whether DoJ policies, regulations, and guidelines were followed in any given matter. That may lead to the discovery of criminal violations, but by no means always. In fact, of its six Divisions, the largest OIG Division is the Audit Division with "200 skilled auditors, program analysts, statisticians and other operational staff."
There is also an Investigations Division that
"investigates alleged violations of fraud, abuse and integrity laws that govern DOJ employees, operations, grantees and contractors. Investigations Division Special Agents develop cases for criminal prosecution, civil, or administrative action."
Again note that these "investigations" are not focused solely on criminal matters--they include civil and administrative matters as well. Often, these investigators are called in to review major investigations to determine whether internal policies and regulations were followed and, if not, what type and degree of culpability would attach: criminal, civil, or administrative. Thus, in the recent case of the FBI Deputy Assistant Director who engaged in unauthorized contacts with reporters, we see that the primary focus was on the DAD's violation of policies and regulations. A potential criminal violation was also identified--Contempt of Court--but prosecution was declined. That was probably, IMO, in line with the way most Contempt of Court violations are handled--administrative rather than criminal action.
As an aside, my own experience with OIG was in the wake of a major CI case. In that instance, as is typical in such cases, the FBI had completed its own investigation and OIG was reviewing the investigation to determine whether the FBI was at fault in its handling of the matter. While it was possible that criminal liability could have been discovered, the focus as always was on whether internal policies and regulations had been followed and also whether OIG might be able to recommend changes or reforms in those policies and regulations.
Therefore, when you see OIG referred to in the context of the Russia Hoax, bear all this in mind. The Russia Hoax is a complicate affair that involves not only FBI and DoJ employees but also employees of other Federal entities as well as foreign nationals and private citizens. Given that OIG can only focus internally, it will in the nature of things be unable to examine all aspects of the Russia Hoax. Even in the area of FISA abuse, it will be unable to examine all the individuals who were involved--some of whom never worked for FBI/DoJ and others who are no longer employed by the Federal government.
The good news, however, is that AG Barr is not limited by OIG's own limitations, which is why he has turned to John Durham to get to the bottom of the Russia Hoax and has sought, and received, extensive powers over declassification (which OIG lacks) from the President. I hope this helps.