That's a good point, and I agree that "registries" just don't cut it. They are wasteful programs, because they track legal gun ownership.
What I fail to get is why it is a bad idea for those who fail to obey our laws to go to jail. If you have a gun, or if it can be proven you carried a gun, without submitting to the legal requirements, you go to jail. This helps police put bad guys who buy black market guns away, without necessarily requiring them to kill a person first.