A person does not have to be present in order to sign off on a vehicle registration. A power of attorney is a legal document that legally allows another person to do so. The vehicle transfer form contains a power-of-attorney section.
In California, powers of attorney are acceptable at the Department of Motor Vehicles for transferring registration. However, they cannot be used to apply for duplicate copies of the title to a vehicle, to disclose odometer mileage, to reassign fights, to appoint or assign duties to an attorney-in-fact, or to delegate administrative duties. Power-of-attorney restrictions may differ in other states.