The CAS ruled in favor of Strasbourg in the transfer wrangle that lasted for over a year.
Al-Koumi's failure to pay Strasbourg 500,000 euros on time to turn Abd-Rabou's loan deal into a permanent one last year prompted the French side to legally react.
Strasbourg lodged a complaint to FIFA to have the player back at their disposal, and their efforts finally bore fruit.
The CAS confirmed that Ismaili failed to meet the deadline for paying Strasbourg their dues and, consequently, Abd-Rabou should return to the French Ligue2 side.
Defiant
Nevertheless, Al-Koumi remains confident that Abd-Rabou would remain with Egyptian League runners-up Ismaili.
"FIFA don't oblige any player to play for any club against his wish," he told Dream Sport.
"Abd-Rabou demanded to annul his contract with Strasbourg in line with article 17 of FIFA regulations.
"This case may take three more years to be settled, during which Abd-Rabou will remain as an Ismaili player."