Quick rule: An image of child pornography is child pornography despite when it was created. In United States v. Peel, 668 F.3d 506 (7th Cir. 2012), the defendant argued that because child pornography was defined as images of children under the age of 16 at the time he took the photos, the images were grandfathered in under current law that would make those images illegal. Not so, said the Seventh Circuit in an opinion by Judge Posner:
If accepted the argument would have the ridiculous consequence of allowing a person who happened to possess pornographic photographs of 16- and 17-year-olds taken before 1984 to market them, giving him a market that being shielded from new competition would offer substantial profit opportunities because after 1984 there could be no further legal production or possession of such pornography.