The right to bear arms is contained within the Second Amendment to the US Constitution. The words, in the final version ratified by the States and authenticated by Secretary of State Thomas Jefferson, are as follows:
"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."The amendment made it into the Bill of Rights along with the right to freedom of speech and religion (the 1st Amendment), protection from unreasonable search and seizure (4th) and due process under the law (5th). Why it is there amongst other unquestionably moral rights is an interesting story.
In 1789 when the Bill of Rights was being written, the United States was a brand new country that had only recently defeated the British in the War of Independence and adopted the US Constitution. There were concerns that the Federal government would become too powerful and abrogate the rights of the States and the people, in the same way as the British Crown and Parliament had done before the Revolution. Congress was divided between the Federalists, who believed that there should be a strong federal government, and the Republicans, who believed in a small federal government that was effectively subservient to the States.
The United States did not have a standing army until 1789. The Continental Army that was led to victory in the War of Independence by George Washington comprised the militias of the thirteen states and was disbanded upon the final defeat of the British at Yorktown except for a small general staff of no more than a few hundred soldiers.
By the time the Bill of Rights was adopted in 1791 there had been both external and internal challenges to the unity of the United States. The risk of renewed war with Great Britain and with revolutionary France, plus the internal Whisky Rebellion and Northwest Indian War, meant many in Congress supported the idea of a strong, standing Federal army. But in order to garner the supermajority of States needed to pass the Constitutional amendments, those promoting the idea had to offer the States something in return. That something was the right to bear arms. The 2nd Amendment was the right demanded by the States to ensure the Federal Government would not be able to use its armed forces to tread upon their rights. Of course one could say the assurance did not work - after all, the American Civil War was primarily about that same issue: whether the Federal Government had the right to over ride the States on the important issue of slavery. And in that case it was a very good thing that the Federal Government won.
Today the issue of Federal vs States rights is more salient than ever. Washington DC and the state capitols are arguing over many important issues - drug enforcement, immigration, health care, etc. The Federal Government has taken upon itself more and more power, including in recent years the power to torture and kill people without any form of judicial process. Many Americans think their government has well-overstepped the constraints that the likes of Thomas Jefferson, Alexander Hamilton and James Madison intended to impose upon it and in view of this, it is understandable that they would be reluctant to give up the right to bear arms.
Seen in this light, the Second Amendment becomes something more noble and reasonable than merely the right of Americans to defend their person and home against criminals (although that, too, is hardly an ignoble right in my opinion).
All of the above doesn't change the fact that American civilians kill far more of their fellow citizens with firearms than any other country on Earth. I agree that America needs to debate the issue but I don't think stricter firearms control alone will do much to address the problem (after all, New Zealand has some of the strictest firearms ownership laws in the world and we have had our share of mass killings). If President Obama wants to introduce tougher gun laws, perhaps he should start talking in the same conversation about limiting the unbridled power of his Government - then more Americans might be more receptive to greater gun control.