Robert Trudeau and Da Da scarf by Dorothy Kristin Hanna, Shreveport , a photo by trudeau on Flickr.
The term Caucasian race (also Caucasoid, Europid, or Europoid) has been used to denote the general physical type of some or all of the populations of Europe. It also may refer to peoples in North Africa, the Horn of Africa, Western Asia (the Middle East), Central Asia and South Asia, says Wikipedia.
Historically, the term has been used to describe the entire population of these regions, without regard necessarily to skin tone.
The concept of a Caucasian race was developed around 1800 by Johann Friedrich Blumenbach, a German scientist and classical anthropologist. Blumenbach named it after the Caucasian peoples (from the Southern Caucasus region), whom he considered to be the archetype for the grouping. He based his classification of the Caucasian race primarily on craniology (the study of skull shapes).
The Caucasus Mts lie on the border of border of Russia and Georgia. They form a barrier that stretches from the Black Sea to the Caspian Sea.
Once part of the Persian Empire, the region is Islamic today.
Where modern day Georgia and Armenia are located is one of the native areas of the wine producing vine Vitis vinifera. Some experts speculate that it may be the birthplace of wine production. Archeological excavation and carbon dating of grape pips from the area have dated back to 7000-5000 BC.
Thus we must assume they call Mr Trudeau a Caucasian because his skull fits the European shape. And because he likes to sip historic wine.