That was the conclusion from the now classic Koper and Roth study that showed no effect of the AWB.
The reasons it failed:
1. The ban only affected cosmetics and equally efficacious guns were continued to be produced - so the ban is stupid or tighten it up to whack all semis.
2. The existence stocks could supply any current level of criminality - so confiscate all guns and mags.
Heard it at the conference where they presented it for the DOJ.
Concluding we don't know if bans work as we really didn't ban and confiscate.