What that wiki page is showing you, is that there is an installed system to identify spent cases, based upon the markings left by firing the cartridge. It says absolutely nothing about any law being in place to mandate such things. It is merely a forensic tool that is widely accepted by various law enforcement entities.
There is no current federal law that mandates that each and every gun bought or sold must submit a spent case to be cataloged.
Many, if not most, handgun manufacturers supply a spent case with the purchase of a new handgun. If you live in NY or MD, this case must be submitted to your PD (IIRC). Other than that, mount it or throw it away (or reload it, if you are a handloader).
To date, not a single crime has been solved in NY or MD with this (expensive) system. Could be that lawful firearms owners don't normally commit crimes?