According to the Wiretap Act of 1968 (18 U.S.C. § 2511.), it’s illegal to secretly record any oral, telephonic, or electronic communication that is reasonably expected to be private. So, for example, recording a conversation with somebody in a bedroom, with the door shut, on private property, without them knowing is technically a federal crime in the loosest sense.
There are, however, a few exceptions to this law that create some sizable loopholes. The biggest being the “one-party consent” rule that says you can record people secretly if at least one person in the conversation consents to the recording, or if the person recording is authorized by law to do it (like police with a warrant). If we go back to our bedroom recording, that means you could record your conversation as long as one person—you—consents to it. Sneaky, eh? But here’s the catch: you have to actually be a part of that conversation. If you were simply recording two other people talking while standing nearby and not saying a word, you then have no consent from any of the parties, and thus it would be illegal.
Twelve states have “two-party (or all-party) consent” laws, meaning you cannot record conversations unless every single person in that conversation gives consent. Those states are:
Washington (not D.C.)