Ahli announced on Friday that their former keeper, who plays for Swiss side Sion, has been banned for four months and fined €900,000 after violating his contract with them.
The Egypt guardian has been at loggerheads with Ahli officials and fans alike since joining Sion without the club's consent in February 2008.
"Al-Hadari will start serving the ban in August," the Red Devils said in a statement on their website.
But Ahli revealed that they were yet to receive an official notification from FIFA's Dispute Resolution Chamber, raising doubts over their claims.
"We can confirm that a decision was reached yesterday regarding the Essam Al-Hadari's case," FIFA Media Department told FilGoal.com via email.
"The respective parties will be notified of the decision taken by FIFA in due course."
It remains to be seen whether the 36-year-old guardian will be suspended.
If the decision content matches Ahli's announcement, Al-Hadari will miss Egypt's World Cup qualifiers against Algeria, Rwanda and Zambia.
However, he will be available for Egypt's Confederations Cup campaign in June.