Congress can compel testimony and documents from the executive branch (and private parties) in aid of its legislative work. Hearings, subpoenas, and contempt citations are how the funding-and-lawmaking branch finds out what is actually happening.
No clause grants an investigative power. The Supreme Court holds it is implied: Congress cannot legislate or appropriate wisely about what it cannot examine (McGrain v. Daugherty, 1927).
Congress, through its committees
Committees unanimous consentDoing business by universal agreement instead of votes. Most Senate floor action happens this way, which is why a single objecting senator has real power.Full definition in the glossary hearings and issue subpoenas under each chamber's rules. Non-compliance can be met with contempt of Congress (criminal referralThe assignment of a newly introduced measure to the committee (or committees) with jurisdiction over its subject.Full definition in the glossary, civil enforcement, or the chambers' dormant inherent power). The recurring counterweight is executive privilege, which shields some presidential communications and is resolved, when pressed, by the courts (United States v. Nixon; Trump v. Mazars).
