According to the United States Citizenship and Immigration Services (USCIS), notaries in California will accept United States passports and passport cards or a foreign passport that has a USCIS endorsement. As passports are government issued, they are considered a legal form of identification. However, the passport must be current to be accepted.
Foreign passports need to have a temporary I-551 stamp from the USCIS to be considered valid. These can be obtained from any USCIS office while waiting for a green card to be mailed. Possible alternate options for those holding foreign passports include a permanent resident card or alien registration receipt card. Residents of Canada and Mexico can simply use their driver's licenses from their home country as valid identification.