The Gunners, who Emery managed between 2018 and 2019, have since withdrawn from the new competition, along with fellow English clubs Manchester City, Manchester United, Chelsea, Liverpool and Tottenham.
And Emery, now in charge of Spanish side Villarreal is against the new competition.
"This is a war for the control of football," Emery told a press conference.
"The clubs have rebelled against control of UEFA.
"My position, in principle, is that I'm against it. It's very risky for football and its essence."