Under U.S. immigration law, foreign citizens seeking entry to the U.S. must present a valid unexpired passport, and if required, a valid unexpired visa issued by a United States embassy or consulate abroad. INA 212(a)(7)(B)(i).

As part of the Western Hemisphere Travel Initiative, beginning January 23, 2007, Canadian citizens seeking entry to the U.S. under TN visa status by air must now present a valid passport. 71 FR 68412 (November 24, 2006). A NEXUS Air card when used at a NEXUS Air kiosk may be used as an alternative to a passport. Id.
Beginning June 1, 2009, citizens of Canada must also present a valid passport when seeking entry to the U.S. under TN visa status at a land or sea port-of-entry. 73 FR 18384, 18403 (April 3, 2008). A trusted traveler card such as FAST, NEXUS, or SENTRI, may be presented in lieu of a passport in order to enter the U.S. at land border ports-of-entry and certain types of arrivals by sea. Id.
There is an exemption to these requirements for Canadian citizen children under age 16 traveling from Canada or Mexico to the U.S. at a land or sea port-of-entry. These individuals (who would be eligible for TD visa status) may also present an original or a copy of a birth certificate, a Canadian Citizenship Card, or Canadian Naturalization Certificate. 73 FR 18384, 18405. There is no similar exception for children when traveling by air. 71 FR 68412, 68416.
Canadian citizens are visa exempt (with a few exceptions) and do not need a visa stamp issued by a United States embassy or consulate in order to enter the U.S. under TN visa status. 8 C.F.R. 212.1 (a).

In addition to a valid unexpired passport, Mexican citizens generally also require a TN visa stamp issued by a United States embassy or consulate in order to enter the United States under TN visa status by air, or at land or sea port-of-entries. 71 FR 68412, 68412; 73 FR 18384, 18404.

Revised March 27, 2012.

Proof of Citizenship & Entry Documents