Michael Oliver is one of four referees who might not be allowed to officiate the World Cup final because of political reasons.

Michael Oliver is one of several referees who might not be able to referee at the World Cup if certain teams qualify. He’s on FIFA’s list of 52 referees, and Anthony Taylor is the other English official at the tournament.
Oliver is set to referee Spain’s quarter-final against Belgium, which could be his last World Cup match. He can’t officiate any games involving England, who are on the other side of the bracket, since referees aren’t allowed to oversee matches with their own country.
He also can’t referee any games involving Argentina, according to BBC Sport’s Dale Johnson, because of the political tensions between the UK and Argentina over the Falkland Islands.
To give some background, the Falklands War was a conflict between the UK and Argentina in 1982 after Argentina took over the islands. The war lasted 74 days and ended with Argentina surrendering and the islands returning to British control. Many soldiers and civilians lost their lives on both sides. Today, Argentina still claims the islands, but in 2013, the islanders overwhelmingly voted to remain a British Overseas Territory.
The football rivalry between England and Argentina is intense. For example, some Argentine players sang a song referencing the Falklands after their recent 3-2 win over Egypt in the World Cup.
If England and Argentina both reach the semi-finals, they would face each other, which means referees like Oliver and Taylor would not be allowed to officiate the World Cup final in New Jersey. The same rule would apply to Argentine referees Yael Falcon Perez, Dario Herrera, and Facundo Tello.
Taylor, who could have officiated the final if Argentina hadn’t been playing, has already handled three matches, including Spain’s 1-0 win against Portugal. There have been concerns from FIFA about Taylor’s impartiality because of earlier anti-Falklands chants by players before the final.
Tello will referee France’s quarter-final in Morocco, making history as the first World Cup match overseen by a full team of officials from the same country. He will be joined by Juan Pablo Belatti and Gabriel Chade as assistants, with Dario Herrera as the fourth official and Cristian Navarro as reserve.
Perez has refereed two group stage matches and a round of 32 game between Switzerland and Algeria, while Herrera has so far led just one match, Belgium vs. Iran.
There are also a few other referees who might miss out if their countries stay in the tournament longer.

