Congress has nullified the common law doctrine of abatement with the federal savings statute (1 USC 19).
--------------------------------------------------------------------------------
[t]he repeal of any statute shall not have the effect to release or extinguish any penalty, forfeiture, or liability incurred under such statute, unless the repealing Act shall so expressly provide, and such statute shall be treated as still remaining in force for the purpose of sustaining any proper action or prosecution for the enforcement of such penalty, forfeiture, or liability.
--------------------------------------------------------------------------------
So you could still be prosecuted for violating a law that has been repealed, so long as the violation took place while the law was in effect. In January 2005, President Kerry (it does have a certain ring to it, does it not?
) could prosecute those who built AWs on the last day the law was in effect. And were dumb enought to post their builds on the internet.