Nobody decides, because there is no referee at any level of this sport. Players call their own violations immediately, and when the two teams cannot agree, the rules say replay the point. That is the written answer, not a friendly compromise.
The score, the positions and the serving order all stay the same. Only the point is played again.
Written by Jakub Popluhar, roundnet coach since 2019, 1,000+ coaching hours, former national coach of Belgium.
This surprises people more than anything else about the sport. Four players, no official, and the players call their own game. The rulebook opens by saying responsibility for fair play falls on the players and that the integrity of roundnet depends on each player upholding the rules.
That is not a gap in the system. It is the system, and it works because everybody knows the procedure for disagreeing.
Call it immediately. Hitting and play infractions, a direct rim hit or contact with the set for example, must be called right after they happen by saying "violation" and stopping play. A hinder is called by saying "hinder" or "violation" and stopping play. There is no calling something three rallies later.
If you cannot agree, replay the point. That is the written rule, not a compromise people invented. When teams cannot determine the legality of a hit, a serve or a call and there are no observers, they replay.
Teammates do not have to agree with each other. The rulebook is explicit and it is the most underrated sentence in the whole document: if three players think one thing and the fourth still disagrees after discussion, that merits replaying the point. One honest player can stop his own team from taking a point.
The score stays, the positions stay, the serving order stays. Only the point is replayed.
Serve faults are the one detail worth knowing. If the point is replayed because of a disagreement about the serve, the server restarts with the fault count they had at the moment of the disagreement. In every other case, the server starts on their first serve again.
After a hinder replay, faults reset.
"Come on Jakub, surely someone cheats?" Sometimes. And that person gets a reputation across a whole continent within one season, because the community is small enough that everybody plays everybody. Social cost turns out to be a stronger enforcement mechanism than a whistle.
There is also a practical argument. A hinder is about whether a player would have reached a ball. The two people who know that best are the two people involved, and no official standing four metres away sees it better.
The habit transfers to the garden, and this is the part worth stealing even if you never enter a tournament. Argue once, replay, move on. Games where nobody keeps a grudge are the games people come back to.
Rim. The ball hits the metal, not the net. Loss of point for whoever hit it. Everybody hears it, so this one rarely gets argued.
Double touch. The same player hit it twice in a row, or the ball ran up the arm. This one gets argued constantly, and it is the main reason the replay rule exists.
Set contact. A player touched the rim, legs or netting during a rally. Loss of point for that player's team, and yes, it counts even when it was clumsy rather than deliberate.
Everything else can wait until you play against people who care about the difference.
No, at any level. Players call their own game.
Replay the point. That is the written rule, not a courtesy.
Immediately, by saying violation or hinder and stopping play. Later is too late.
Yes. The rules explicitly allow it, and one disagreeing player is enough for a replay.
No. Score, positions and serving order stay. Only the point is replayed.
Rim hit, double touch, and touching the set during a rally.
Next time you are sure and they are sure, replay it. It costs one rally and saves the evening.