; failure to register (a) In general Whoever— (1) is required to register under this Act; (2) (A) is a gun offender by reason of a conviction under Federal law (including the Uniform Code of Military Justice), the law of the District of Columbia, Indian Tribal law, or the law of any territory or possession of the United States; or (B) travels in interstate or foreign commerce, or enters or leaves, or resides in, Indian country; and (3) knowingly fails to register or update a registration as required under this Act, shall be fined under title 18, United States Code, or imprisoned not more than 6 months, or both. (b) Affirmative defense In a prosecution for a violation under subsection (a), it is an affirmative defense that— (1) uncontrollable conditions prevented the individual from adhering to this Act; (2) the individual did not cause the creation of such circumstances to disregard the requirement to comply