## Facts

- The United States, in connection with a federal grand jury investigation, applied ex parte for an order under 18 U.S.C. §§ 3121–3127 authorizing use of a pen register and trap-and-trace device (as a “device” or “process”) on a specified email account.
- The application sought only non-content transactional data associated with email communications, including sender and recipient email addresses, dates and times, and other routing or header-type information.
- The government represented that it would not collect the contents of communications (e.g., subject lines or message bodies).
- A magistrate judge questioned whether the Pen Register Act authorized pen register/trap-and-trace orders for email accounts and required additional briefing.
- The government sought district-court review, requesting that the magistrate judge’s order be vacated and that the pen register/trap-and-trace order be issued.

## Issues

1. Whether the Pen Register Act, 18 U.S.C. §§ 3121–3127, authorizes a court to issue a pen register and trap-and-trace order directed to an email account to obtain non-content addressing and routing information.
2. Whether the government’s application satisfied the Act’s requirements for issuance of an ex parte order.

## Decision

- The district court held that the Pen Register Act authorizes installation and use of a pen register and trap-and-trace device (including as a “process”) to capture non-content “dialing, routing, addressing, or signaling” information associated with an email account.
- The court vacated the magistrate judge’s order requiring additional briefing.
- The court granted the government’s application, limited to non-content information as defined by the statute.

## Legal Principles

- Under 18 U.S.C. § 3127, a pen register or trap-and-trace device may be implemented as a “device” or “process” that records or decodes “dialing, routing, addressing, or signaling” information for wire or electronic communications, excluding contents.
- The Pen Register Act applies to electronic communications and is not limited to telephone networks; it reaches email transactional data analogous to telephone signaling information.
- Pen register/trap-and-trace authority is limited to non-content metadata (e.g., sender/recipient addresses and routing data) and does not permit interception of email contents (including subject lines and message text).
- For issuance under 18 U.S.C. § 3122, the government must certify that the information likely to be obtained is relevant to an ongoing criminal investigation; once the statutory prerequisites are met, the court’s duty to issue the order is mandatory.

## Conclusion

The court ruled that the Pen Register Act permits ex parte orders for collection of email addressing and routing metadata, so long as the collection excludes contents, and that a compliant relevance certification requires issuance of the order.


In re Application of the United States for an Order Authorizing the Installation & Use of a Pen Register & a Trap & Trace Device on E-Mail Account, 416 F. Supp. 2d 13 (D.D.C. 2006)