I think what they meant was no registry tying gun owners to particular guns. Once they tied the marks to the gun, then they could use the same trace process as exists today. That is from the manufacter, to the wholesaler, to the retailer, to the first buyer. After that they lose the trail. Needless to say, criminals don't buy their guns from legitimate retail dealers. No telling how many times a gun could have changed hands before it fell into those of a criminal.
It seems to me that the real problem the "system" has is not catching criminals, but rather convicting and sentencing them in a timely manner and then keeping them locked away from decent folk until they are no longer a threat.
Of course, but that's not what this crap is about - its about screwing the law abiding gun owner, once again. No gun law has ever disarmed a criminal - its about finding creative ways to make a mess for the law abiding citizen wishing to exercise Constitutional rights. These laws produce a "chilling effect" as the lawyers say, on people who want a gun but when they find out what a hassle it is to get one, simply give up. That's how it is in California with the may issue CCW laws; in my county, I don't bother to even consider applying for a carry permit. The legislature wants to create a mountain of BS piled on top of a Constitutional right so that no one (outside of the elites) will be able to surmount it.