The Administrative Court upheld on Monday the death sentences for six members of Ansar Beit Al-Maqdes (ABM), which were handed down last October by a military court.
The ruling by the Administrative Court comes more than two months after the prisoners were executed.
The death sentences were carried out by hanging on 17 May based on murder convictions in a military trial in October of 2014.
In November 2014, the lawyer representing the six members, Ahmed Helmy, brought the case to the administrative court prior to the execution, but the judge adjourned the hearing.
This postponement resulted in the hearing not be held until after the execution was already carried out.
Helmy argued that the executive decision by President Sisi to approve the death sentences in May 2015 was unconstitutional, Al-Ahram Arabic news website reported.
The case became known as the "Arab Sharkas" case, named after the village in the Qalyubia governorate, north of Cairo, in which two military officers were killed during an anti-terrorist raid by security forces in March 2014.
ABM has claimed responsibility for many of the attacks against army and police forces in Egypt following the ouster of Islamist president Mohamed Morsi in July 2013.