The French chess federation has suspended Sébastien Feller, a 20-year-old grandmaster, his team-mate Cyril Marzolo, 32, and Arnaud Hauchard, 39, the French team captain. It said they used mobile text messages, a remote chess computer and coded signals to beat the opposition.
The fraud, which took place during last September's Chess Olympiad in Khanty-Mansiysk, Russia, has rocked the chess world, which prides itself on its code of honour.
Rival teams have been known to accuse each other of cheating, but in this case the whistle-blower was the French federation's own vice president, Joanna Pomian.
She became suspicious when she found a text message addressed to Mr Marzolo, which read: "Hurry up and send me some moves." It was sent from Russia by Mr Hauchard during the competition.
She examined Mr Marzolo's itemised phone bill and found he had sent more than 150 text messages to Mr Feller during the tournament, plus 30 to Mr Hauchard. Unable to look at their contents due to a privacy ruling, she and the federation nevertheless remained "convinced" the players had cheated.
The federation said the system required Mr Marzolo to follow the game via the internet. He logged the moves into a chess computer then texted its suggested moves to Mr Hauchard in codes within phoney telephone numbers.
The captain communicated these to Mr Feller during his match by standing next to a particular player who represented a pre-agreed number and a figure. Mr Feller could follow his captain's movements to know which piece to move and where.
Mr Feller won three games at the tournament, enough to earn him a gold medal and €5,000 (£4,400).
According to Laurent Vérat, the federation's director-general, Mr Feller and Mr Hauchard owned up to the fraud in October, but "refused to sign any documents".
"The only thing that mattered to them was that the affair didn't get out," he told Le Parisien.
Mr Feller and Mr Marzolo were handed down five-year suspensions while Mr Hauchard received a life ban from being team captain or a coach.
The three deny any wrongdoing and have appealed against the ruling.