Quinton Birdinground Jr., 38, is scheduled to appear Aug. 23 before U.S. District Judge Susan Watters in Billings.
Federal Defender David Ness said Wednesday he expects to ask for a sentence of time served - meaning Birdinground would be released - but has not made a final decision.
Birdinground is serving 24 years in federal prison for assaulting his estranged girlfriend and killing Emerson Pickett during an argument in Crow Agency after a night of drinking.
The original sentence included 10 years for using a firearm during a violent crime.
Watters this month threw out that conviction, saying the violent crime law was so vague as to be unconstitutional. She cited a 2015 Supreme Court ruling.
Birdinground will be resentenced on two remaining counts: second-degree murder and assault resulting in serious bodily injury.
Birdinground has been incarcerated for more than 15 years since his arrest in February 2003.
If he were released, Ness said Birdinground likely would remain under supervision of federal authorities for some period of time.
He was charged with killing Pickett after finding the victim with Birdinground's estranged girlfriend, Leitha Yellowmule. Yellowmule's hand was grazed by the same bullet that killed Pickett, prosecutors said.
The defense had argued at Birdinground's trial that the shooting was accidental.
In her order throwing out the charge of using a firearm during a violent crime, Watters wrote that neither second-degree murder nor assault is itself considered a "crime of violence" under federal law. That's because they may have been committed recklessly rather than intentionally, as is required to be considered a violent crime.
"Birdinground used a firearm, but not 'during and in relation to a crime of violence,' " Watters wrote.
U.S. Attorney Kurt Alme declined to say whether prosecutors will request a new sentence that would keep Birdinground in prison.
Alme's office is reviewing the case with the Office of Solicitor General at the Justice Department for a possible appeal of Watters' decision, but that can't be filed until after sentencing, he said.
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