Rioch gave way to the unknown Frenchman in 1996 when he was axed by Arsenal after barely a year in the Highbury hotseat.
“He has been such a great ambassador for the club that he surely deserves the right to make the decision to leave his own decision.
“Arsene has done magnificently well for the Arsenal and, for me, he will most certainly leave with his head held high."
Rioch added: "It's a club that will always mean a lot to me and not just because I had the privilege of managing Arsenal.
“When I was a kid, I used to go and watch the Arsenal in the 1960s and watch games at Highbury. It's a very special club."