The sources which requested anonymity said that the firmís name is Eversheds LLP which specializes in international law.
Repeated attempts to get comment from Eversheds were unsuccessful.
In 2005 Sudanese officials said that Khartoum contemplated using a western law firm to counter the ICC but that after reviewing options it was ďtoo expensiveĒ.
In mid-July the ICC prosecutor Luis Moreno-Ocampo announced that he is seeking an arrest warrant for Al-Bashir.
The ICCís prosecutor Luis Moreno-Ocampo filed 10 charges: three counts of genocide, five of crimes against humanity and two of murder. In early October ICC judges have officially started reviewing the case in a process that could possibly drag on to next year.
After failing to secure a suspension of the ICC move Sudanese officials said they would deal with the ICC íindirectlyí through a third country that is a member of the ICC or a law firm.
Sudan insists that it is not bound by the ICC since it is not a member of the court.
However there is little the law firm can do without the war crimes suspects appearing before court. The ICC rule does allow trials in absentia.
The Sudanese president is not officially charged yet as the judges are reviewing the evidence and at this stage defense lawyers are not allowed to file motions to interrupt this process.
To issue an arrest warrant on the charges filed by the prosecutor the ICC judges have to be convinced that there are Ďreasonable groundsí that the individual(s) committed the crimes listed in the filing.
Once the individual(s) are in custody a confirmation of charges hearing is held before a trial is commenced and defense lawyers are allowed to challenge the evidence. The judges could confirm or decline the charges for which an arrest warrant was issued.
Sudan has not ratified the Rome Statute, but the UN Security Council (UNSC) triggered the provisions under the Statute that enables it to refer situations in non-State parties to the world court if it deems that it is a threat to international peace and security