Appellee (Defendant US Atty General's Office) Response Brief was filed in Schrader.
What the government is saying is that because at common law, any misdemeanor offense could have been punished by a term of imprisonment exceeding two years, 18 U.S.C. § 922(g)(1) applies.
According to the government, it makes no difference if you could prove that no simple assault & battery (fistfight) ever received such a sentence, it could have.
The government is also arguing that once convicted of a crime, however slight, you are a criminal for life... Even after 40 years of an otherwise exemplary life.