A child traveling with only one birth parent needs a letter of consent from the other parent before they are allowed to leave the country, according to the U.S. Customs and Borders Protection. This is due to the increasing concern over child pornography or incidents of child abductions, in which one divorced birth parent in a disputed custody case tries to steal the child from the other.
Unless the child is traveling with both parents, the adults accompanying the child, which may consist of grandparents, uncles, aunts, sisters or brothers, must present a letter of consent signed by both parents to the customs or immigration officials. The letter of consent must include the basic information (who, what, where, when, why) and the contact information of the parents or of the absent parent. If both parents are dead or are indisposed to sign a letter, the legal guardian of the child or anyone who has the legal right to make decisions on the child's behalf can sign the parental consent. In such cases, additional documentation, such as a birth certificate, death certificate, court decisions or other relevant paperwork, may be required, according to the U.S. Customs and Borders Protection.
Not all countries require one to have a letter of parental consent, but it is highly advisable to bring one and to have it notarized in order to prevent any travel disputes when traveling abroad.