(3)
Whoever violates paragraph (2) after having been previously convicted of a violation punishable under that paragraph shall be imprisoned for any period of years not more than 10 years but not less than 2 years, and fined in accordance with the provisions of this title, or both.
The provisions of this section shall not become effective until 90 days after the final regulations implementing this section are published in the Federal Register. The provisions of this section shall not apply to any matter, or image therein, produced, in whole or in part, prior to the effective date of this section.