After Katrina, one of the first responses by the NOPD was to confiscate
private citizens' guns. They used the gun registry.

One of the many reasons I live in NH, where we have very, very low crime
(other than routine violations of FARs, which no one polices), and fences
are usually to keep the horses on the property:

http://www.nraila.org/GunLaws/StateLaws.aspx?ST=NH