A military court of appeals turned down on Monday a challenge filed by Jamaa Islamiya leader Safwat Abdel Ghani and four others against their prison sentence, therefore upholding the sentence.
Abdel Ghany was sentenced, alongside four other Jamaa Islamiya leaders, to a year's labour and a 500 Egyptian-pound fine for attempting to flee to Sudan.
The five Islamist leaders were arrested in Aswan last July. They were also accused of trespassing on a military zone.
The defendants denied their knowledge of the nature of the area where they were arrested in their challenge to the verdict. They said there was no sign clarifying that the area was a military zone. They also argued that the court trying them lacked the proper jurisdiction to do so being a military court and since they are civilians.
Article 204 of Egypt’s 2014 constitution allows referring civilians to military trials "in cases which represent a direct assault on armed forces institutions, their camps or anything that falls under their authority, alongside assaults on military or border zones, and military institutions, vehicles, weapons, ammunition, documents, secrets, public funds, or factories."
The article was strongly condemned by civil society organisations and a number of political movements before the constitution passed.
No Military Trials for Civilians, a group campaigning against referring civilians to military tribunals, has rallied protests against this article as well as previous legislations which allow the military trial of civilians.
The Jamaa Islamiya is a hardline Islamist group which was implicated in several militant attacks in Egypt during the 1990s, before its jailed leaders renounced violence in 1998.
Following the January 2011 uprising which toppled former President Hosni Mubarak, the group formed a political party, the Building and Development Party, and forged strong ties with ousted Islamist President Mohamed Mursi's administration.