You and a foreign amateur radio operator both have a local friend without amateur radio certification engaged in radio communication. Who is considered a third party?

In amateur radio terminology, a "third party" is defined as anyone who is not the primary licensed operator of the transmitting or receiving station. Because the two licensed amateur radio operators are considered the first and second parties in the communication, any unlicensed individuals speaking over the radio are third parties. Therefore, both your uncertified local friend and the foreign operator's uncertified local friend are considered third parties. They are participating in the communication but do not hold the authorization for the station. Distractors might lead you to believe only the Canadian or only the foreign uncertified person is a third party, but the definition universally applies to any non-certified person participating in the communication at either end of the radio link.