Mexico's policy is typical. Mexican law requires that if only one parent (or grandparent, or other guardian) is accompanying a minor under 18 into Mexico, they must bear a notarized letter from the child’s other parent (or guardian) granting permission to enter Mexico with the child, including the dates of travel, the accompanying adult’s name, contact information, and a notarized signature.

A consular officer at the U.S. Department of State's Office of Children's Issues verified the facts required by most countries from a 'permission to travel' letter, and reiterated that a parent's notarized signature and identification for the child (birth certificate or passport) were both essential.