Sakho withdrew from Senegal's Africa Cup of Nations squad, citing a back problem, but came on as a substitute to score the winner at Ashton Gate in the fourth-round tie before his country were knocked out of the AFCON.
West Ham were subsequently fined 100,000 Swiss Francs and given a reprimand, but avoided expulsion from the Cup, despite FIFA's own regulations suggesting they should have been.
A City statement read: "Bristol City FC notes FIFA's decision with regards to the Disciplinary Committee's case against West Ham United and their player Diafra Sakho.
"The club is disappointed with the penalty handed down by the FIFA Disciplinary Committee and is considering its options."
FIFA's rules on the matter state: "If a club refuses to release a player or neglects to do so, the FIFA Players’ Status Committee shall furthermore request the association to which the club belongs to declare any match(es) in which the player took part to have been lost by the club concerned.
"Any match contested according to the cup system shall be regarded as having been won by the opposing team, irrespective of the score."
Watch every match of the Africa Cup of Nations LIVE on British Eurosport HD or sign up to Eurosport Player and follow the action on mobile, tablet and other devices: www.eurosportplayer.com
