Your argument is a full of holes as Poddster's socks............

First of all, without convictions, you have a legal right to own a firearm, unless you are deemed mentally unstable.

Second, it's not a gun registration, it's a background check..........how do we know who is a felon or who is mentally unstable without investigating their background?  If gun registration is a violation of the fourth amendment, so is vehicle registration.

Third.........why make it even easier for criminals to obtain firearms?

Fourth........gun laws don't deny citizens weapons, they only deny certain weapons.........Australia has a gun ownership percentage of under 5%, yet most feel quite safe in their homes.........so your argument has no validity.