In February 2007, Warner Bros. hired Kieran and Michele Mulroney to write a script for Justice League, which they handed in that June to positive feedback from the studio. George Miller signed to direct in September 2007, while the studio hoped filming would start before the 2007–2008 Writers Guild of America strike. In addition, the studio was considering filming Justice League completely in motion capture, similar to Beowulf. Barrie Osbourne was to produce, with a $220 million budget.
Filming was supposed to start in February 2008, in Australia, where post-production would also be conducted. Some shooting was to take place at Sydney Heads, while local colleges were scouted. But in January 2008, Warner Bros. announced the film was on indefinite hold, allowing an options lapse for the cast. The studio felt the script needed perfecting, which was impossible because of the writer's strike. As soon as the strike ended, Warners wanted to start filming in mid-April 2008. In February 2008 it was announced that production would go to Canada, despite Miller's wishes to keep production at Fox Studios Australia. The Mulroneys are currently rewriting the script.
Marit Allen was originally hired as costume designer, but she died in November 2007. Weta Workshop took over costume design, a decision which opens the possibility of their sister company, Weta Digital, doing the visual effects.
While a cast for the film was never officially declared, various news brokers were able to confirm a number of Miller's casting choices, for which he chose predominantly younger actors who he had hoped would "grow into their roles" over the course of a film trilogy. The decision to cast lesser-known actors has received negative feedback from comic book fans on the internet. Brody, Common, Gale and Hammer will have to physically train for their roles. In October 2007, roughly 40 actors and actresses auditioned for the League, among them; Joseph Cross, Michael Angarano, Max Thieriot, Minka Kelly, Adrianne Palicki and Scott Porter.
Concerning the eponymous Justice League, Adam Brody had been cast as Barry Allen / The Flash, with D. J. Cotrona as Superman, rapper Common as John Stewart / Green Lantern, Australian supermodel Megan Gale as Diana Prince / Wonder Woman, Armie Hammer was cast as Batman, Santiago Cabrera as Aquaman, Australian actor Hugh Keays-Byrne as Martian Manhunter, and Aussie starlet Teresa Palmer as Talia Al Ghul. A number of different actors were fleetingly associated with the project; Jessica Biel had turned down the role of Wonder Woman, while Mary Elizabeth Winstead auditioned. Teresa Palmer and Shannyn Sossamon were also interested, while Christina Milian, a comic book fan, offered her services for the role. Columbus Short turned down the role of Green Lantern, which rapper T.I. was also rumored for.
From February 2007 until April 2008, the much maligned project was subject to rumours before eventually being put on an indefinite hiatus; in a recent interview, producer Joel Silver stated that Justice League "has been tabled. In August 2008 director George Miller was quoted saying "the flick's production, initially planned for Oz, has been moved offshore, with a plan to resume filming next year. However, on August 22, The Wall Street Journal reported that Warner's new plan is to release four individual solo movies within the next three years before doing a multiple character movie, much like rival Marvel is reportedly doing with their Avengers film. While Warner Bros. Pictures Group President Jeff Robinov confirmed that one of those films will be a Superman reboot, it is likely that among the other three, there will be a sequel to the successful Batman movie The Dark Knight as well as two movies introducing fresh DC Comics characters to the big screen. It has since been confirmed that one of the other two movies will be about Green Lantern.
In December 2008, there were rumors that director Miller was off the project. They were dispelled by a representative of the filmmaker, however, describing the movie's status as "being seriously worked on.
IESB reports that Chris Nolan is quickly becoming DC and Warner Bros. go-to guy for looking out for their major A-list titles, as the Dark Knight director may soon find himself in the director's chair for a JLA movie, after he finishes work on Batman 3.
At the Wonder Con, they hinted that 2011 will have Green Lantern, 2012 will have a third Batman and a Flash movie titled "The Flash". 2013 will hold the Superman reboot titled The Man of Steel and possibly a Wonder Woman movie all leading to a Justice League movie set in the same universe much like Marvel Studios' Universe. It would potentially feature Christian Bale and Ryan Reynolds reprising their roles as Batman and Hal Jordan, respectively.
Later that year IESB reported that DC will build their characters in their own worlds, slowly but surely intertwining them with each new film likely starting with the upcoming Green Lantern until a Justice League film. They also said Batman would naturally be the first superhero to appear, and the early continuity is looking like this: Batman Begins is being specifically referred to as "Action Comics #1." Translation: Nolan's Batman is the first (and only) superhero around. and The Dark Knight is being referred as "Action Comics #2." Green lantern would be "Action Comics #3" followed by Batman 3, Man of Steel, The Flash, Wonder Woman, Aquaman, and then a Justice League movie. It has been rumored that Warner Bros. is planning a Justice League movie without Superman and Batman.
In January 2008, Warner Bros. announced the film was on indefinite hold, allowing options lapse for the cast. The studio felt the script needed perfecting, which was impossible because of the 2007-2008 Writers Guild of America strike.
In February 2008 it was announced that production would go to Canada, despite George Miller's wishes to keep production at Fox Studios Australia. The filmmakers are still adamant for a mid-2009 theatrical release date, and hope to have filming start in mid-July 2008. 
In October 2013, George Miller's script for Justice League: Mortal was leaked online