Assuming your crazy idea to ban ownership of lawfully owned guns would ever happen (it won't) how exactly do you propose to remove the 200-300 million guns already in circulation? Connecticut tried this, this year, and it failed miserably. They passed a new law after Sandy Hook banning assault weapons, magazines larger than 10 rounds and requiring people to register their guns. About 50,000 people complied out of an estimated 500,000 guns that would fall under the new law. That's a 10% compliance rate. Thank sweet little baby jesus that they passed that law. I'm sure everyone is MUCH safer now.
