Federal law bans felons from possessing firearms, but doesn't expressly say whether this applies only to people who know they are felons. Usually this doesn't matter, since it is the rare felon who's confused about whether he's a felon. But U.S. v. Kitsch (E.D. Pa. Aug. 1, 2008) (Dalzell, J.), involves such a case:

[Footnote: The facts are largely undisputed. Because we must decide whether Kitsch's version of the story would, if credited by the jury, justify acquittal, we resolve any factual disputes in his favor for purposes of this motion.] In 1988 and 1989, Kitsch was cooperating with law enforcement officials in Atlantic County, New Jersey in an investigation against a man named Dino Starn who was, among other things, growing marijuana in a barn on his property. As a means of helping the narcotics officer with whom he was working obtain evidence against Starn, Kitsch set a small, smoky fire on the windowsill of the barn and then promptly called the fire department. When the fire department arrived, it found the marijuana growing in the barn and Starn was later charged.

As a result of the fire, Kitsch was charged with third-degree arson, a felony under both New Jersey and federal law. He pled guilty to the state offense after meeting with law enforcement officials who told him they would set aside the conviction and Kitsch could live as though the event had never happened. Although he served a thirty-day custodial sentence on Sundays, Kitsch avers that he truly and reasonably believed that his conviction had either been set aside or expunged. [More factual details omitted. -EV]

The district court concludes that under federal law Kitsch would be guilty only if he knowingly possessed a gun knowing that he was a felon, and that Kitsch is entitled to a jury instruction that "in order to convict Kitsch, the Government must prove beyond a reasonable doubt that he knew or was willfully blind to the fact that he had a prior felony conviction that had not been set aside or expunged."

The district court's reasoning chiefly rested on the general presumption against strict liability, to its reading of this statute, and to its reading of past precedents interpreting similar statutes; based on this, the court was willing to reject an out-of-circuit court of appeals precedent, United States v. Langley, 62 F.3d 602 (4th Cir. 1995), that held the contrary. But the court also suggested that the Second Amendment, as interpreted in D.C. v. Heller, supported its conclusion:

A statute that imposes criminal penalties for the exercise of an enumerated constitutional right despite defendant's reasonable belief in good faith that he has complied with the law must, at the very least, raise constitutional doubts. Post-Heller, the Government's desired construction of Section 922(g)(1) imposes just such a burden on defendants who, for whatever reason, reasonably believe that they are not felons within the statutory definition. Faced with a statute that raises this sort of doubt, it is "incumbent upon us to read the statute to eliminate those doubts so long as such a reading is not plainly contrary to the intent of Congress."

The trial is yet to come; we'll see whether the court's ruling helped Mr. Kitsch. For a similar opinion concluding that a constitutional right to bear arms -- there, both the Second Amendment and a right to bear arms under the state constitution -- counseled against reading a gun control law as imposing strict liability, see State v. Williams, 148 P.3d 993 (Wash. 2006) (which I blogged about here).