A former Austin neo-nazi’s Supreme Court case has become more complicated.

The U.S. Supreme Court heard a re-argument last week of Sam Johnson, the former Austin man with ties to white supremacist groups who was sentenced to 15 years in prison on a weapons charge. His sentence was based in part on a prior conviction for having a short-barrel shotgun.

At issue is whether possession of a short-barreled shotgun constitutes a “violent felony” under the Armed Career Criminal Act, which meant Johnson was required to receive a mandatory minimum sentence of 15 years.

The court heard Johnson’s case in November, but ordered a re-argument to take place April 20 to determine whether the law’s wording is unconstitutionally vague.

In his plea agreement, Johnson admitted he possessed a 7.62x.39 caliber, semi-automatic assault-style rifle on Nov. 4, 2010. Because he is a felon, Johnson was prohibited from possessing firearms or ammunition at any time.

Federal officials believed Johnson was amassing weapons and hundreds of rounds of ammunition as part of a plan to attack the government and minorities.

Johnson’s criminal history includes a number of convictions in Mower County: attempted simple robbery in 2000, simple robbery in 2007, possession of a short-barreled shotgun in 2007, and sale of a simulated controlled substance in 2007. Johnson also has a Hennepin County conviction for felony theft in 1999.

Since at least three of Johnson’s prior felony convictions were for crimes of violence or serious drug crimes, sentencing in this current case was subject to the Armed Career Criminal Act, which mandates a minimum of 15 years in federal prison. Johnson faced a maximum sentence of life in prison.

According to a federal affidavit, Johnson was a former member and Minnesota leader of the National Socialist Movement, a white nationalist group, and had gone on to form his own group, called the Aryan Liberation Movement. He once held rallies in Austin.

Another man, Joseph Benjamin Thomas, 42, of Mendota Heights, was indicted on drug charges and later investigated for his alleged ties to Johnson and possible terroristic plots.

Thomas also told an undercover FBI agent he considered himself a “domestic terrorist” instead of an American and would risk his life for the white supremacist movement in the event of a “race war,” an FBI affidavit said.