One persistent suggestion in the post Newtown conversation about gun control is a law requiring the registration of all guns, even so called "long guns" like the rifle Adam Lanza used in the school killings. Lost in the discussion: Canada tried it and gave up, discovering like several other nations that attempting to identify every gun in the country is an expensive and ultimately unproductive exercise. Criminals, of course, don't register their guns. And even law abiding citizens tend to ignore registration when it comes to long guns mostly used for hunting and target shooting.

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