President Anwar El-Sadat on the day of his assassination, 6 October 1981 (Photo: AP)
Mohamed Mokhtar arrived in Egypt on Monday after spending twenty years in exile in the United Kingdom.
Al-Gamaa Al-Islamiya member Mokhtar fled Egypt in the early 1990s to escape arrest over the assassination of President Anwar Sadat. He was tried in absentia and sentenced to seven years in jail for his role in the killing.
In the UK he established a centre for spreading Islam.
Under Egyptian law there is a ten-year statute of limitations, meaning Mokhtar will not be arrested upon his return to the country.
President Sadat was assassinated during a military parade on 6 October 1981 by Islamist soldiers angry at Egypt's 1979 peace treaty with Israel.
Among those convicted of the killing were Aboud and Tarek El-Zomor, leading members of Al-Gamaa Al-Islamiya, who were released in March 2011 when the Supreme Council of the Armed Forces ordered the release of 60 political prisoners who had served 15 or more years.
Assassination mastermind Lieutenant Khaled Islambouli was executed by a firing squad in 1982.
Al-Gamaa Al-Islamiya, whose members were persecuted during Mubarak era, established the Building and Reform Party following the January 25 Revolution. The party ran in the 2011 parliamentary elections as part of the Islamic Alliance alongside the Nour and Asala Salafist parties, which won around 27 percent of seats in the People's Assembly.