You don’t know whether that referee would be biased or not. Even if it’s home court, it’s still possible that a referree be objective. So you really don’t know if it can be rigged. It’s hard to tell.
If there is a match against Real Madrid and the match is in Santiago Bernabeu, be assured that the referees will be on Real Madrid's side. Overall, it's a well-known fact that referees are biased in favor of the team that has match on their own stadium. It's also a well-known fact that referees are more forgiving to superstars and in some cases, to the teams of where these superstars play. For example, Messi is a superstar and every referee tries to avoid yellow or red card to him because if he gets benched, that will cause a huge protest in players since most of them come to watch his performance. When it comes to world cup, everyone wants Messi or Cristiano to win, so they treat Argentina and Portugal better but today it's not the thing to my mind since these two players are almost retired.