For a call recording to be lawful, federal law  and most states require at least one party to the conversation to consent to the recording. However, many states go further, requiring two-party (or all-party) consent for a call to be lawfully recorded.
As the following list demonstrates, navigating the state law nuances of two-party consent for recording calls can require some finesse.
Requires prior consent from all parties to record a confidential in-person, telephone, or video communication. 
However, case law indicates that where a person communicating is made aware that the conversation is being monitored or recorded, there may be no violation because there is no objectively reasonable expectation of privacy.  Moreover, by continuing with the conversation after being so warned, consent is given by implication. 
Allows call recording if:
- all parties have consented to the recording,
- recording is preceded by a verbal notification which is recorded as well, or
- recording is accompanied by an automatic tonal warning. 
Requires two-party consent for recording telephone or other private conversations. 
However, a district court held the state law was meant to emulate its federal equivalent,  so one-party consent may, in some circumstances, satisfy the consent requirement.
Requires prior consent from all parties to record an oral communication. 
However, the law does not cover when the person communicating had no reasonable expectation of privacy,  which may occur when the parties are notified at the outset that the call will be monitored or recorded.
Requires all parties to consent to recording either an in-person or transmitted communication when at least one party intends the communication to be of a private nature under circumstances reasonably justifying that expectation. 
Requires all parties to a communication to consent to the recording. 
However, Maryland courts have interpreted this to be limited to situations where parties have a reasonable expectation of privacy. 
Prohibits secretly recording or secretly hearing wire or oral communications. 
Therefore, where parties to a communication are notified beforehand of the recording, the recording may fall outside the statute on grounds that the recording is no longer being done in secret.
Prohibits recording private conversations without consent of all parties.  A “private conversation” is one in which a person reasonably expects to be free from casual or hostile intrusion or surveillance. 
Michigan has also been argued to have an exception for recordings made by participants to the conversation,  but a district court subsequently declined to follow this reasoning and rejected the existence of a participant-exception. 
The Michigan Supreme Court has been silent on this issue, so the participant-exception issue has not been settled.
Prohibits recording communications by use of a hidden device without the knowledge of all parties to the conversation. 
However, this prohibition does not apply if the parties are notified of the recording, even if they do not expressly consent. 
Requires consent of all parties for interception of communications. 
However, consent may be implied when the circumstances around a situation demonstrate that a person was aware they were being recorded. 
Requires two-party consent for recording in-person conversations, but only one-party consent for recording telecommunications. 
A “telecommunication” is, in part, a transmission of pictures and sounds by aid of wire or similar connection between the transmission’s origin and reception points, and it includes all instrumentalities, equipment, and services incidental to such transmission. 
Therefore, Oregon may, in certain circumstances, operate as a one-party consent state.
Prohibits intercepting oral communications unless all parties consent. 
To qualify, an oral communication must have been uttered by a person possessing an expectation that such communication is not subject to interception under circumstances justifying such expectation. 
Prohibits recording private communications or private conversations unless all parties give prior consent. 
However, consent may be considered obtained whenever one party announces to all other parties that such communication or conversation is about to be recorded, so long as that announcement is also recorded. 
 18 U.S.C. § 2511.
 Cal. Pen. Code § 632(a).
 Kearney v. Salomon Smith Barney, Inc., 39 Cal.4th 95 (2006).
 Conn. Gen. Stat. § 52-570d(a).
 Del. Code Ann. tit. 11, § 1335(a)(4).
 U.S. v. Vespe, 389 F.Supp. 1359 (1975).
 Fla. Stat. § 934.03(2)(d).
 Fla. Stat. § 934.02(2).
 720 ILCS § 5/14-1.
 Md. Code Ann., Cts. & Jud. Proc. § 10-402.
 E.g., Malpas v. State, 116 Md.App 69 (1997).
 Mass. Ann. Laws ch. 272, § 99(B)(4), (C)(1).
 Mich. Comp. Laws § 750.539c.
 People v. Stone, 463 Mich. 558 (2001).
 Sullivan v. Gray, 117 Mich.App. 476 (1982).
 AFT Michigan v. Project Veritas, 378 F.Supp.3d 614 (2019).
 Mont. Code Ann. § 45-8-213(1)(c).
 Mont. Code Ann. § 45-8-213(2)(iii).
 N.H. Rev. Stat. Ann. § 570-A:2.
 State v. Locke, 144 N.H. 348 (1999).
 Rev. Stat. Ann. § 165.540(1).
 Rev. Stat. Ann. § 165.535(4).
 18 Pa. Cons. Stat. Ann. § 5704(4).
 18 Pa. Cons. Stat. Ann. § 5702.
 RCW § 9.73.030(1).
 RCW § 9.73.030(3).