In the anime series Gundam Seed, ZAFT created a series of advanced mobile suits based on technology reverse-engineered from the captured Earth Alliance G Project suits. Like their EA predecessors, the ZAFT Gundams were armed with advanced beam weaponry and protected by Phase Shift armor. However, a additional technology was incorporated as well: the Neutron Jammer Canceller, which countered the effects of the ubiquitous N-Jammers and allowed these suits to be powered by nuclear reactors. This gave them almost limitless combat endurance, even with Phase Shift armor activated.

One of these suits was the ZGMF-X09A Justice Gundam. It was the first and most conventional of the series, armed with beam sabers, beam boomerangs, head-mounted CIWS guns (which, foreshadowing what would later become standard practice, were much smaller in calibur than those of other mobile suits), and a high-energy beam rifle. In addition, the Justice Gundam carried a large detachable Fatum-00 backpack, which could be remotely controlled or used as a sublfight lifter. The Fatum-00 was also well-armed with a pair of beam cannons and multiple machineguns. However, the suit's most powerful weapon was the optional METEOR (Mobile suit Embedded Tactical EnfORcer) support system, a large mobile weapons platform with powerful thrusters and an even more powerful armament of battleship-calibur beam cannons, large beam swords, and dozens of heavy missile launchers that was designed specifically for the Justice Gundam and ZGMF-X10A Freedom Gundam. Having a tall sensor spine on the top of its head, like the GAT-X303 Aegis Gundam, the Justice Gundam is most likely also a commander mobile suit.

Late in CE 71, Athrun Zala, former pilot of the GAT-X303 Aegis Gundam, was assigned the Justice Gundam with the mission to either recapture or destroy its stolen sister unit, the Freedom Gundam. Instead, however, Athrun joined forces with the Freedom Gundam's pilot, his old friend Kira Yamato, in defending neutral Orb from an Earth Alliance attack, then returned to space along with the Archangel and Orb battleship Kusanagi, and met up with the support vessel Eternal, which had been stolen by Lacus Clyne and her supporters, led by former ZAFT commander Andrew Waltfeld, and which carried both METEOR units. Atrhun and Kira used the METEORs' firepower to thwart an Earth Alliance nuclear missile attack on the PLANTs, and Athrun also destroyed the GAT-X131 Calamity Gundam. Then, on the final day of the war, Athrun self-destructed the Justice Gundam inside the doomsday laser GENESIS, and was rescued by MBF-02 Strike Rouge pilot Cagalli Yula Athha.

In CE 73, ZAFT began developing an upgraded version so far referred to as Knight Justice Gundam.

Specifications

ZGMF-X09A Justice Gundam

Manufacturer: Zodiac Alliance of Freedom Treaty
User: Zodiac Alliance of Freedom Treaty, Clyne Faction
Unit type: prototype assault mobile suit
First Deployment: May 17, Cosmic Era 71
Head height: 18.56 m
Weight: Max gross 75.4 t
Special equipment: Phase Shift armor, Neutron Jammer Canceller, backpack/subflight lifter, hardpoint for docking with METEOR unit
Powerplant: Ultracompact nuclear fission reactor, power output rated at 8826 kW
Armament: MMI-GAU1 "Sagittus" 20mm CIWS x4, MA-M01 "Lacerta" beam saber x2, RQM51 "Bassel" beam boomerang x2, Fatum-00 backpack/subflight lifter (M9M9 "Cervus" turret machinegun x2, MA-4B "Fortis" beam cannon x2, GAU5 "Volucris" machinegun x4) x1, MA-M20 "Lupus" high-energy beam rifle x1, shield x1
Pilot: Athrun Zala

Knight Justice Gundam

Manufacturer: Zodiac Alliance of Freedom Treaty
User: Zodiac Alliance of Freedom Treaty
Unit type: prototype assault mobile suit
First Deployment: Cosmic Era 73
Head height: unknown
Weight: unknown
Special equipment: Phase Shift armor, modified N-Jammer Canceller
, backpack/subflight lifter,
Powerplant: Ultracompact nuclear fission reactor, power output unknown
Armament: MMI-GAU1717 12.5mm multi-barrel CIWS x4, 1 backpack/subflight lifter ,M106 "Amfortas" plasma beam cannon x2, MA-7B "Super Fortis" beam cannon x2, MMI-GAU2 "Picus" 76mm machinegun x2, MA-M941 "Vajra" beam saber x2, MA-BAR70 high-energy beam rifle x1, shield x1
Pilot: Athrun Zala