Very simple.
Every regime that has confiscated privately owned firearms started with background checks and a "gun registry"
Background checks are a liberal feel good measure, criminals will simply find other ways to obtain weapons. The only people who will submit to background checks are already law abiding citizens.
It is very clear that Obama favours firearm confiscation and bans. The only things that stand in his way are little things like the Constitution and political opposition.
It always amazes me that liberals will support policies that make them feel good about themselves even if they have no or the opposite effect in the real world.
Banning and confiscating firearms from law abiding citizens can only serve to increase criminal gun violence.
I'm not against background checks when they do not involve a registry. You can create a system where people can verify they have no criminal record and use that system for ANY purpose, not only purchasing firearms. Maybe you only want to rent to tenants who have no criminal background, maybe you are hiring a cashier who will handle money, or a maid who will go into homes to clean them, or a babysitter to look after your kids, or a coach for a kids sports team. All reasons to want to know somebody is clean. No need to tie it to firearms.
Then rewrite anyone selling a firearm to perform a background check. They can even get a confirmation receipt that they did so. Government does not need to know WHY the check was performed.
So this wouldn't create any registry and it would be generally useful in any case you need to know somebody had a clean history.
While it won't stop criminals from getting guns it would allow police to prosecute those who knowingly sold the gun to a crook and eliminate the plausible deniability is "he told me he was clean, I had no reason to suspect".
But the claim that this would stop the majority of criminals from getting guns? Nope.