A consent letter is recommended for all cross-border travel, even for a day trip, if the child will be travelling alone, with only one parent, with friends or relatives or with a youth group.
A letter of consent, preferably in English and notarized, from the other parent or signed by both custodial parents. The letter should say: "I acknowledge that my child is traveling outside the country with the name of the adult with my permission."
Is a minor travel consent form required for domestic travel? No, a minor travel consent form is not required for domestic travel within the U.S. However, it is recommended that parents and/or legal guardians carry a notarized letter of consent when traveling with a child.
In California, when there is no court order regarding custody in place, both parents have equal rights to the children. However, California law requires written consent from the other parent before removing minor children from the state, whether for relocation or vacations.