Assume a man is indicted for lying on a form that he did not use drugs, in order to purchase a handgun.
Furthermore assume Drug user cannot be barred from owning guns, US court rules.
Update: Assume the indicted man's defense cites said ruling as a defense. Is the ruling, that drug users can not be barred from owning guns, an affirmative defense or is there a better label?
An affirmative defence is a defence that must be put forward by the defendant or accused, with elements that they are required to prove. These would normally need not even be considered unless the analysis has already concluded that the plaintiff / prosecution has preliminarily met their burden.
An affirmative defence is in contrast to a defence that simply argues that the plaintiff or prosecution has failed to meet the plaintiff/prosecution burden of proving the elements of the claim/crime to the required standard.
Self-defence is an affirmative defence to assault. Fair use is an affirmative defence to copyright infringement.
"I didn't create the infringing work" is not an affirmative defence. It simply attacks the plaintiff's burden to prove that you were the infringer.
"I didn't mean to kill the deceased" is not an affirmative defence. It simply attacks the prosecution's burden to prove intent for murder.
A court ruling that drug users cannot be barred from owning guns is not a form of defence. It is just a wholly different category. A court ruling is simply a statement of the law—in this case, about what government may or may not do.
The holding from the court ruling might be used as part of an argument that the lie on the form was not material or in some other way failed to make out an element of the offence. If this is how the ruling is used, that is not an affirmative defence; it would simply be attacking the prosecution's position that the elements of the offence were present.
Court holdings may also be used to argue that it would be unconstitutional to apply a particular criminal statute to a certain circumstance. This would not arise in the posture of a technical "defence" in the narrow sense of the word, but rather, as a pre-trial motion. In this scenario, many people would nonetheless refer to it as a "defence" colloquially.
