
It would be difficult but I would take it a step further. The referee can’t be from the same continent as a team currently playing in the game. This in addition to the original post. For example if the referee team is predominantly South American but not from Argentina that’s fine but a South American ref can’t officiate an Argentina game in the World Cup.
All I’m saying is that there aren’t that many qualified referees and a rule like this would essentially block all referees from certain countries (the ones that consistently make it pretty far) from refereeing most of the tournament. Finding enough fully qualified referees to ref the group stage only from countries that didn’t qualify for the World Cup would prove to be difficult.
Furthermore, I’m willing to bet that there’s a correlation between number of world-class referees from a country and how good that country is at soccer. I think it would be unfair to block tons of qualified referees from refereeing the World Cup based solely on their country of origin.