LOUISVILLE, Ky. — Federal prosecutors argue a law used to convict a former soldier on civilian charges of murder and rape in Iraq is constitutional and allows the government to pursue former soldiers who otherwise would escape prosecution.

The Military Extraterritorial Jurisdiction Act is being challenged by Steven Dale Green, 24, of Midland, Texas, who was convicted of raping and murdering 14-year-old Abeer Qassim al-Janabi and killing three of her family members in March 2006 while deployed to Iraq.

The former 101st Airborne Division soldier was the first soldier charged under the little-used MEJA. He was convicted by a civilian jury in Kentucky and got five life sentences.

Green argues the law allowing his prosecution is unconstitutional because it gives the executive branch of government too much leeway over who to prosecute.

Federal prosecutors disagreed in an 86-page brief filed Thursday.

“The MEJA does not empower the government to choose between a military or civilian courtroom; instead, it simply permits the government to choose a civilian courtroom over no courtroom at all,” Department of Justice attorney Michael Rotker wrote.

Rotker’s brief paints Green as the instigator of the rape and slayings, differing from the testimony of his co-conspirators at trial which put another soldier at the center of the plot. One of Green’s attorneys, Darren Wolff of Louisville, said efforts to put his client at the center of the conspiracy are irrelevant to the appeal.

“What we’re arguing about is the constitutionality of the law,” Wolff said. “The law they prosecuted him under is unconstitutional.”

Green is also contesting whether the military validly discharged him before he was charged in civilian court. Rotker wrote that any minor problem with Green’s discharge wasn’t enough to invalidate his dismissal from the Army for a personality disorder.

Green and four other soldiers based at Fort Campbell, Ky., were investigated after Abeer was raped and her body set afire.

Green had been honorably discharged with a personality disorder and returned to the U.S. by the time the Army charged him in June 2006. The military refused to allow him to re-enlist, and Green was indicted as a civilian.

The four other soldiers received sentences ranging from five years to 110 years based on their acknowledged roles in the attack. One soldier has been released from military prison after serving 27 months. The others are eligible for parole in 2016.

Though Green was the first soldier charged under MEJA, a former Marine who was charged after Green was acquitted of murder in Iraq. In recent months, former private contractors have been prosecuted under MEJA, with two having pleaded not guilty Wednesday to shooting deaths in Afghanistan.