18 U.S.C. § 3121 — General prohibition on pen register and trap and trace device use; exception

(a) No one may install or use a pen register or a trap and trace device without first getting a court order. That order must come under section 3123, the Foreign Intelligence Surveillance Act, or a certified agreement with a foreign government. (b) This ban does not apply to phone or internet providers in three situations. First, when they use these devices for their own operation, maintenance, or testing, or to protect their rights, property, or users from abuse. Second, when they record that a communication happened, to protect themselves, another provider, or a user from fraud or abuse. Third, when the user has consented to it. (c) A government agency that is allowed to use these devices must use available technology to limit what it records. It may capture only dialing, routing, addressing, and signaling information. It may not capture the actual content of any communication. (d) Anyone who knowingly violates the ban in subsection (a) faces a fine, up to one year in prison, or both.

The source credit indicates that this section was added by Public Law 99-508, title III, § 301(a), enacted October 21, 1986, and published at 100 Stat. 1868. The credit further shows that the section has been amended on three subsequent occasions: by Public Law 103-414 in 1994, Public Law 107-56 in 2001, and Public Law 115-141 in 2018. Each amendment is cited with its corresponding Statutes at Large reference, but the source credit does not itself describe the substance of these changes beyond what appears in the current text. Public Law 99-508 is commonly known as the Electronic Communications Privacy Act of 1986. This Act is generally understood to have updated federal wiretap and surveillance law to address technological developments in electronic communications, including computer transmissions and pen register/trap and trace devices, which earlier statutes had not contemplated. The broader legislative effort of that era is often described as an attempt to balance law enforcement's investigative needs with privacy protections in an evolving communications landscape. The record does not establish the specific legislative intent behind this particular section's provisions—such as the exceptions in subsection (b) or the technology limitation in subsection (c)—beyond what the statutory text itself conveys. Similarly, the specific purposes behind the 1994, 2001, and 2018 amendments are not detailed in the source credit provided, and no legislative history is available here to explain those changes with certainty.