Former Blackwater guards, from left, Dustin Heard, Evan Liberty, Nicholas Slatten and Paul Slough.

The U.S. Justice Department asked a full federal appeals court Monday to review a decision to throw out the first-degree murder conviction of one former Blackwater Worldwide security guard and the sentences of three others in shootings that killed 14 unarmed Iraqi civilians in Baghdad in 2007.

Acting Solicitor General Jeffrey B. Wall approved the decision, which was expected and filed by appeals lawyers for the department's criminal division, to seek a full court review by the U.S. Court of Appeals for the D.C. Circuit, after a three-judge panel ruled Aug. 4.

The panel said a trial court "abused its discretion" in not allowing Nicholas A. Slatten, 33, of Sparta, Tenn., to be tried separately from his three co-defendants in 2014 even though one of them said he, not Slatten, fired the first shots in the massacre. Slatten was convicted of murder

By a separate, 2-to-1 vote, the panel also found that the 30-year terms of the others convicted of manslaughter and attempted manslaughter — Paul A. Slough, 37, of Keller, Tex.; Evan S. Liberty, 35, of Rochester, N.H.; and Dustin L. Heard, 36, of Maryville, Tenn. — violated the constitutional prohibition against "cruel and unusual punishment."

They received the enhanced penalty because they were also convicted of using military firearms while committing a felony, a charge that primarily has been aimed at gang members and never before been used against security contractors given military weapons by the U.S. government.

The Justice Department filing called the panel's sentencing finding "as wrong as it is unprecedented," saying the U.S. Supreme Court has upheld longer sentences for lesser crimes.

"By its plain terms, the statute applies to defendants, who used their most fearsome weapons to open fire on defenseless men, women, and children," the department said. "Far from being unconstitutional, these sentences befit the 'enormity' of defendants' crimes."

The government also cited "legal and factual errors" in the ruling granting Slatten a retrial, noting the "great international consequence" of his prosecution for "a humanitarian and diplomatic disaster."

A retrial in "a prosecution of this magnitude (including reassembling the many Iraqi witnesses) poses considerable and uncommon challenges," the department wrote, urging the full court to reconsider "in a case of such exceptional importance."

In their own filing Monday, attorneys for the four men asked the full court to toss out the case on jurisdictional grounds and so reverse the panel's finding that civilian contractors supporting the Pentagon could be prosecuted under the Military Extraterritorial Jurisdiction Act.

The attorneys could not be reached for comment. A group representing family members and friends of the four tweeted a statement from Slatten last month that said, "Public outrage may be our only chance at true justice for all four of us. While it may be too early to seek pardons for my brothers from President Trump, he especially needs to hear from you."

Staff writer Ann E. Marimow contributed to this report.