Barcelona have won their appeal to the Court of Arbitration for Sport (Cas) to keep Argentina's Lionel Messi out of the Olympic football tournament.
Cas ruled that the 21-year-old, as well as Werder Bremen's Diego and Rafinha of Schalke, can be prevented from taking part in the Beijing Games.
The Barca forward was keen to take part but the clubs argued the Olympics was not part of the international calendar.
Fifa said it was "surprised and disappointed" by the decision.
Cas found that Fifa's position was based on custom rather than law, meaning clubs could not be forced to release their players.
The court ruled there was "no specific decision of the Fifa executive committee establishing the obligation for the clubs to release players under 23 for this tournament".
A statement added: "Cas calls upon the goodwill and the good sense of Fifa and the clubs to find a reasonable solution with regard to players who wish to represent their country in the Olympic Games."
Messi is already in Beijing with the Argentina squad, who play the Ivory Coast on Thursday when the men's football tournament gets under way.
In response to the decision by Cas, Fifa president Sepp Blatter said: "Fifa is surprised and disappointed by this decision, but we respect it.
"Nevertheless, I appeal to the clubs. Let your players take part in the Olympic Games. It would be an act of solidarity in perfect harmony with the Olympic spirit.
"It would be wonderful for the players, for the fans and for the game itself.
"I regret that the Cas has not taken the Olympic spirit into consideration."
Blatter has already said Fifa will conduct a review of Olympic football regulations to ensure the London Games in 2012 are not hit by more club-versus-country rows.
Fifa ruled on 30 July that clubs must release players aged 23 or under for the Olympics if a nation requests them.
The world governing body had said: "The judge determined that the international match calendar is not of relevance in establishing whether clubs are obliged to release players for the men's Olympic football tournament.
"Taking part in the Olympic Games is a unique opportunity for all athletes of any sporting discipline.
"It would not be justifiable to prevent any player younger than 23 from participating in such an event if his representative team had qualified."
I appeal to the clubs. Let your players take part in the Olympic Games
Sepp Blatter
But Barcelona, Werder Bremen and Schalke reacted by lodging their appeal against Fifa's ruling.
Barca want Messi for the first leg of their Champions League third qualifying round tie on 12 August.
AC Milan prevented Brazil from picking their star player Kaka in the Olympics, although the Italian club's new signing Ronaldinho as well as Manchester United's Anderson were both included in Brazil's 18-man Olympic squad.
Real Madrid have asked Brazil to release Robinho from Olympic duty because of a suspected groin injury. The 24-year-old has more than 50 Brazil caps and is a reported target for Chelsea.
Cas ruled that the 21-year-old, as well as Werder Bremen's Diego and Rafinha of Schalke, can be prevented from taking part in the Beijing Games.
The Barca forward was keen to take part but the clubs argued the Olympics was not part of the international calendar.
Fifa said it was "surprised and disappointed" by the decision.
Cas found that Fifa's position was based on custom rather than law, meaning clubs could not be forced to release their players.
The court ruled there was "no specific decision of the Fifa executive committee establishing the obligation for the clubs to release players under 23 for this tournament".
A statement added: "Cas calls upon the goodwill and the good sense of Fifa and the clubs to find a reasonable solution with regard to players who wish to represent their country in the Olympic Games."
Messi is already in Beijing with the Argentina squad, who play the Ivory Coast on Thursday when the men's football tournament gets under way.
In response to the decision by Cas, Fifa president Sepp Blatter said: "Fifa is surprised and disappointed by this decision, but we respect it.
"Nevertheless, I appeal to the clubs. Let your players take part in the Olympic Games. It would be an act of solidarity in perfect harmony with the Olympic spirit.
"It would be wonderful for the players, for the fans and for the game itself.
"I regret that the Cas has not taken the Olympic spirit into consideration."
Blatter has already said Fifa will conduct a review of Olympic football regulations to ensure the London Games in 2012 are not hit by more club-versus-country rows.
Fifa ruled on 30 July that clubs must release players aged 23 or under for the Olympics if a nation requests them.
The world governing body had said: "The judge determined that the international match calendar is not of relevance in establishing whether clubs are obliged to release players for the men's Olympic football tournament.
"Taking part in the Olympic Games is a unique opportunity for all athletes of any sporting discipline.
"It would not be justifiable to prevent any player younger than 23 from participating in such an event if his representative team had qualified."
I appeal to the clubs. Let your players take part in the Olympic Games
Sepp Blatter
But Barcelona, Werder Bremen and Schalke reacted by lodging their appeal against Fifa's ruling.
Barca want Messi for the first leg of their Champions League third qualifying round tie on 12 August.
AC Milan prevented Brazil from picking their star player Kaka in the Olympics, although the Italian club's new signing Ronaldinho as well as Manchester United's Anderson were both included in Brazil's 18-man Olympic squad.
Real Madrid have asked Brazil to release Robinho from Olympic duty because of a suspected groin injury. The 24-year-old has more than 50 Brazil caps and is a reported target for Chelsea.
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