Golf is the only sport where TV viewers act as rules officials. If a fan sees a violation and it turns out to be true, a player must be penalized. How replay comes into play in other sports and who can invoke it:
---
FOOTBALL
Officials can use video evidence to decide certain plays when coaches (not fans) challenge them. A replay official automatically reviews turnovers, scoring plays and some other loose-ball situations and can request the on-field officials review evidence.
---
BASEBALL
Umpires use judgment for all calls, but can use video on home runs to determine whether the ball fair or foul, or if it cleared the fence.
---
BASKETBALL
Referees can check courtside monitors to determine if a basket was a 3-pointer or not, but no calls may be directly influenced by fans.
---
HOCKEY
NHL officials monitor games and initiate replays from a ''war room'' in Toronto to determine if a goal has been scored or not. There is no outside mechanism for a TV crew or viewer to alert someone of a rules violation.
---
Sources: NBA, MLB, NHL officials; NFL.com, NHL.com
