The Alaves striker has had his initial request to turn out for the Atlas Lions rejected on March 13 and he appealed to the CAS in his latest attempt.
Madrid-born El Haddadi who has a Moroccan father and Spanish mother made his competitive bow - a 15-minute cameo - for La Furia Roja in their 5-1 thrashing of Macedonia on September 8, 2014, during the Euro 2016 qualifiers.
However, he has not made another senior appearance for the former world champions and is desperate to join Herve Renard’s setup ahead of the big summer.
Fifa rules restrict players from switching allegiance once they have made their international competitive bow, whether or not they hold dual nationality.
“The Court of Arbitration for Sport (CAS) has registered an appeal filed jointly by the football player Munir El Haddadi and the Moroccan Football Federation against the Fédération Internationale de Football Association (FIFA) and the Spanish Football Federation,” read a statement from CAS.
“Munir El Haddadi and the Moroccan Football Federation are challenging the decision issued on 13 March 2018 by the FIFA Players’ Status Committee in which their request to have the sporting nationality of Munir El Haddadi changed from Spain to Morocco was rejected.”
A panel of three arbitrators will be selected to hear the case and according to CAS, a decision is expected by mid-May for "the player’s sporting nationality to be decided prior to the commencement of the 2018 World Cup.
“Following the hearing, the panel will deliberate and issue a decision in the form of an arbitral award.”
Should El Haddadi’s case prove successful, he faces the prospect of featuring against his then former national team in the colours of his new country at the World Cup as Spain and Morocco, alongside Portugal and Iran are placed in Group B.