According to the 2nd Amendment of the Constitution, "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed ."
Note the purpose of "Arms" ownership is to have a well-regulated militia for protection...
In Obama's speech on gun control today, the number 3 thing to do was: "We're going to do more to help those suffering from mental illness get the help that they need." I would be curious to hear how he is going to do this.