What power does the US Department of Justice (DOJ) Inspector General (IG) have to compel testimony?
All Inspectors General have a power to issue subpoenas. However, such subpoenas are administrative subpoenas. "An administrative subpoena under U.S. law is a subpoena issued by a federal agency without prior judicial oversight." "Administrative subpoenas have most commonly been issued by the Offices of the Inspector General of various federal agencies."
"Neither the head of the establishment nor the officer next in rank below such head shall prevent or prohibit the Inspector General from initiating, carrying out, or completing any audit or investigation, or from issuing any subpoena during the course of any audit or investigation." See 5a U.S. Code § 3(a).1
For the DOJ IG, that subpoena power is restricted in those cases that "require access to sensitive information". See 5a U.S. Code § 8E(a)(1).2
Can the DoJ IG subpoena anyone? If so, who?
Apparently, any person who may have information related to a specific investigation. However, "procedures other than subpoenas shall be used by the Inspector General to obtain documents and information from Federal agencies." See 5a U.S. Code § 6(a)(4).3
[I say apparently due to absence of any clause, except in one case: Specifically, the DOD IG "shall use procedures other than subpoenas to obtain attendance and testimony from Federal employees." See 5a U.S. Code § 8(i)(1).] 4
What consequences would someone refusing to testify, answer questions, or produce documents requested by the DoJ IG face?
A United States district court proceeding; "... which subpoena, in the case of contumacy or refusal to obey, shall be enforceable by order of any appropriate United States district court". See 5a U.S. Code § 6(a)(4).5 The DOJ enforces IG subpoenas and may choose to not pursue the matter.
In practice it is difficult and time consuming to proceed through the court system, so the subpoenas are rarely enforced. The House passed, and sent to the Senate H.R.4917 "to grant inspectors general subpoena authority to compel the attendance and testimony of witnesses." Subpoenas under the new authority would have been enforceable unless the Attorney General objected. The bill died in a Senate committee.
1 5a U.S. Code § 3.Appointment of Inspector General; supervision; removal; political activities; appointment of Assistant Inspector General for Auditing and Assistant Inspector General for Investigations.
2 5a U.S. Code § 8E.Special provisions concerning the Department of Justice.
3, 5 5a U.S. Code § 6.Authority of Inspector General; information and assistance from Federal agencies; unreasonable refusal; office space and equipment.
4 5a U.S. Code § 8.Additional provisions with respect to the Inspector General of the Department of Defense.