CRS Report via FAS –Congressional Subpoenas: Enforcing Executive Branch Compliance, March 27, 2019. “Congress gathers much of the information necessary to oversee the implementation of existing laws or to evaluate whether new laws are necessary from the executive branch. While executive branch officials comply with most congressional requests for information, there are times when the executive branch chooses to resist disclosure.

When Congress finds an inquiry blocked by the withholding of information by the executive branch, or where the traditional process of negotiation and accommodation is inappropriate or unavailing, a subpoena—either for testimony or documents— may be used to compel compliance with congressional demands. The recipient of a duly issued and valid congressional subpoena has a legal obligation to comply, absent a valid and overriding privilege or other legal justification. But the subpoena is only as effective as the means by which it may be enforced.

Without a process by which Congress can coerce compliance or deter non-compliance, the subpoena would be reduced to a formalized request rather than a constitutionally based demand for information. Congress currently employs an ad hoc combination of methods to combat non-compliance with subpoenas. The two predominant methods rely on the authority and participation of another branch of government. First, the criminal contempt statute permits a single house of Congress to certify a contempt citation to the executive branch for the criminal prosecution of an individual who has willfully refused to comply with a committee subpoena. Once the contempt citation is received, any prosecution lies within the control of the executive branch. Second, Congress may try to enforce a subpoena by seeking a civil judgment declaring that the recipient is legally obligated to comply. This process of civil enforcement relies on the help of the courts to enforce congressional demands. But these mechanisms do not always ensure congressional access to requested information…”