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Justin Law (ジャスティン＝ロウ, Jasutin Rō), known by the moniker "Executioner (死刑, Shikei)", was the 17-year-old Death Scythe, previously in charge of the DWMA Western Europe Branch. Subcumbing to Madness and becoming an agent of the Kishin Asura, he defects and formerly affiliated himself with Noah's Group but later defects to the Clown Army.
Prior to his descent into Madness, Justin portrayed himself in a polite and zealous manner. His worship and faith in Death was reflected in his mannerisms, speaking expressively to his allies. Loyal to the DWMA, he often follow Death's orders to the letter and valued the lives of students within the academy and was willing to kill those that threaten either those two things. When faced enemies like Giriko, he had a notion of subtly mocking and chastising them. 
However, his struggle to understand his dilemma involving his tendency into solitary and inability to place enough trust to make friends with others while counting only on a god caused him internal issues. Because of this and his poor understanding of Order and what "lies beyond it" that it "crushed" him caused him to descend into Madness according to Franken Stein. After his descent into Madness courtesy of the Clown, his personality became much more darker and despicable. His willingness to kill now extended to his former allies under the allegiance of Asura with little to no remorse and adopted a misogynistic view on women.
Justin appears as a slim, young man with short, loosely styled blonde hair, light-blue eyes. In his initial appearance, his attire consists of a white shawl that encompasses all around the upper part of his body from his neck to elbow length, a deacon's cross with Death's mask on it over the shawl and has visible headphones (also with Death's mask on them) that emerge from the shawl and into his ears. Under the shawl is a black, ecclesiastical robe. The sleeves of the robe have white crosses on them which expand when Justin partially transforms and his guillotine blade emerges from the cross. The front of the robe also has a portion made of grey fabric that almost makes the robe look like a double-breasted overcoat. This section of the robe has six visible black buttons on it with cross designs that are symmetrically separated on opposite sides of the grey part to the robe. Finally, he wears a pair of black pants, loafers, and a white Zucchetto for a hat. While on Lost Island, he also sported gloves with crosses on them.
After Justin falls to Madness, he undergoes an alignment change which lightly affects his wardrobe. He still appears in his priestly attire and Zucchetto; however, the Death worship vanishes, and is altered to a Kishin worship theme. The Deacon's cross with Death's mask design on it changes to a Kishin three-eye pendant instead, in addition to the same Kishin eyes being featured on Justin's sleeves (instead of the white crosses) and earphones (again, instead of Death's mask). After being damaged by Tezca Tlipoca's Solar Ray, he gained a massive scarring in which appears like a constant, perpetual flame. In addition to this, his left lip, having been burned off, allows more of his teeth exposed. This appearance makes him constantly appear more insane and malicious.
His soul appears a blue colored soul sporting a guilotine on top of it, referencing to his Guillotine weapon form.
Justin can be described as a very competent prodigy, having been the youngest Death Scythe in the history of Death Weapon Meister Academy and having been able to gather 99 evil human souls and slayed a witch without the need of a Meister. His skill in battle has allowed him to rival that of Giriko, a fellow Demon Weapon skilled without a Meister and whom spent 800 years gathering power. Franken Stein considered Justin dangerous enough to warrant the need for himself and Marie Mjolnir to fight as a pair, lightly reminding the then angered Death Scythe he as capable of becoming a Death Scythe on his own unlike herself.
- Prayer (祈り, Inori): As a Priest and believer of gods, Justin is capable of performing a prayer. While praying to either Death (and later Asura), he can amplify his own Soul Wavelength and execute powerful attacks. Although he usually does perform a prayer before executing some of his techniques, it is not a requirement.
- Law-Abiding Silver Gun (法を守る銀の銃, Rō Abaidingu Shirubāgan):A powerful technique in which after performing a prayer, Justin's guilotine blade is pointed at a target and sends a powerful ray of light made up of his Soul Wavelength capable of cleaving the Oldest Golem's head.
- Law-Abiding Silver Gun Radiant (法を守る銀の銃「放射」, Rō Abaidingu Shirubāgan Reidianto): A variation of Law-Abiding Silver Gun that, instead produces a widely dispersed beam capable of pushing Giriko himself back.
Full-Weapon Transformation (全身武器, Zenshin Buki): Being a Demon Weapon, Justin is capable of transforming himself into a weapon. However, his weapon form, known to be a guillotine, has not been seen. Despite this, he has a tendency to have a usage of partial transformations.
- Stationary Type (設置型, Setchi Gata): Justin is known as a Stationary type of weapon and as such, is capable of setting traps due to his weapon-related powers. As such, he can create guillotine-like traps in which traps enemies and bisects them with a blade like that of a real guillotine.
- Holy Cross Chop (聖十字手刀, Hijiri Jūji Shuto; FUNimation "Saint Cross Knife"): An attack in Justin attacks with his arms being partial blades from his guildotine weapon form, creating an offensive cross formation. Such an attack was lethal, capable of of critically damaging Giriko had he not used his defensive Chain ability.
- Carcan Bras (首枷の籠手, Karukan Bura; FUNimation "Neck Shackle Guard"): A technique in which Justin immobilizes his opponent's limbs by transforming his arm into the headlock component of a guillotine.
Enhanced Durability: Justin has been seen able to take blunt hits from both Marie Mjolnir's powerful punches and direct hits from Franken Stein using Mjolnir; this is despite the fact that his speed far surpasses his own after the latter utilized Lightning Rope.
Master Autonomous/Hand-to-Hand Combatant: Despite becoming a Death Scythe at the age of thirteen, Justin is an extremely skilled Demon Weapon who fights on his own without a Meister, using a combination of his fighting skills and Demon Weapon powers. He's been known to fight evenly with Giriko, another Demon Weapon whom also possesses autonomous combat skill and is evenly matched. His skill is highly regarded, with Franken Stein warning Marie Mjolnir of his ability and urging her to transform. He also easily killed Auntie during the Battle of the Moon, who gave the Clown Kaguya difficulty.
Lip Reading: Justin has admitted to being able to read the lips of others, allowing him to communicate without having to remove his earbuds.
- Executioner: After his prior descent into madness and subsequent adoption of the doctrines belonging to the Kishin Asura, Justin Law procures the ability to merge with a Clown, through a mere snap of his fingers and the uttering of a single command. The process itself is a relatively simple one, requiring only that the Clown deconstruct its body and proceed to surround Justin in order to complete the unison but the alterations the transformation results in are nonetheless drastic because of this.
- Madness Wavelength (狂気の波長, Kyōki no hachō): Because of a Clown's nature in sharing the same wavelength as the Kishin, the Executioner form is capable of having a Madness Wavelength in which can be used.
- Chain Blades: This forms can make use of the chain blades in which replaces his hands, capable of fighting opponents as well as deflect attacks like Vector Arrow with accurate swings.
Enrolled within Death Weapon Meister Academy, his devotion to the worship of Death was known and made it difficult for him to make friends within the Academy. Understanding his problem, Death assisted Justin in making him a Death Scythe.
When he was thirteen years old, he had successfully became a Death Scythe, having done so without a Meister and was hailed as the youngest Death Scythe in history as well as being called "The Executioner who appears with Deafening Sound". This exploit made him somewhat of a legend in DWMA. After becoming a Death Scythe, he often spent time with Tezca Tlipoca, though was unable to comprehend what he was saying due to his bear mask blocking his lips.
Soul Eater NOT!Edit
When a trio of NOT Class students (Anya Hepburn, Tsugumi Harudori, Meme Tatane) are lost within the many halls and passages of Death Weapon Meister Academy, Justin stands ready to assist them though intimidates them with his sudden appearance and interpreting his words with darker intents. He's later present as Clay Sizemore reveals the possible suspects of recent thefts in the DWMA and the rise of Traitors, including the Witch, Shaula Gorgon.
Justin later arrives in Death City with his fellow Death Scythes, Death, and Death the Kid himself as the older Death God gives Shaula Gorgon an ultimatum. He witnesses Shaula being struck down and Kid himself taking custody of her soul.
- Justin's attack, "Law Abiding Silver Gun", is a reference to B. Ichi, another manga by Soul Eater creator Atsushi Ōkubo. In B. Ichi, the character Yohei Nanami uses a gun called the 'Law Abiding Silver Gun,' a gun that is shaped like a dog's head.
- In the anime, Justin always listens to the same song, "Step Up."