Lenient gun ownership laws of the U.S.

Once again, lenient gun ownership laws of the U.S. have been blamed in the wake of the very recent gun-shooting massacre in Tuscon, Arizona.
However, widespread gun ownership and lenient laws governing it may be one of the main reasons why the U.S. is capable of being a great nation. That is, civilians RESERVE the power and forces to tame the elected government, as I heard.
But, that is a very very subtle and controversial issue that my little mind, which is untrained in Political Science, cannot handle.