There are far more private security officers in the United States than sworn police officers, and almost none of them have the authority the uniform implies. This article explains what a private guard or investigator can actually do, which turns out to be roughly what any other private citizen can do, plus a narrow merchant's detention privilege and whatever a property owner has delegated. It explains why that gap between apparent and actual authority is where nearly all the liability lives. It covers the licensing architecture that varies wildly by State, the shopkeeper's privilege and its strict conditions, the state-action doctrine that occasionally converts a private guard into a constitutional defendant, and the surveillance rules that catch investigators who learned the trade before the statutes caught up. It covers the Fair Credit Reporting Act problem that most investigators do not know applies to them. It closes with negligent security, the contract terms that allocate this risk, and what a well-run operation actually documents.