FARGO (AP) - A Fargo man sentenced to two life prison terms without parole in a murder case is now facing trial on federal weapons charges.

Aron Nichols pleaded not guilty Thursday to three illegal weapons charges. He's accused of possessing a short-barreled shotgun and a machine gun.

U.S. Magistrate Judge Karen Klein set trial for Sept. 15.

Nichols and his fiancee, Tamara Sorenson, were convicted in May for the deaths of a Wells County couple. The bodies of 70-year-old Donald Willey and his 67-year-old wife, Alice, were found in their burned farm home near Sykeston in April 2007. Authorities say the murders resulted from a dispute about visitation rights to a grandchild.