Ultimately you then rely on the power of influence, you hope that your players realise that a multi million euro fine & a substantial ban from European competition would then encourage players to report this to their clubs out of duty to protect their clubs - I mean much as I know footballers are mercenaries these days I'd like to think if someone approached any player on Man United's squad they'd be straight on the blower to Fergie. Ultimately you can't cage the players up but you need to have them understand that this is unacceptable - immediate lifetime bans for all players (google Pete Rose to see that in action) convicted of match fixing, no compromise, they will never receive a license from FIFA to play or coach as a professional again.