The text of the second amendment provides for the right of citizens to bear arms, with the specific motivation of "A well regulated militia being necessary to the security of a free state".
While a federal law or policy for universal arms regulation would almost certainly infringe upon the sovereignty of states, it is by this constitutional provision the duty of the government to ensure that any arms-bearing militia is well-regulated.
The Obama administration should encourage legislation that requires states to establish specific regulations for their arms-bearing militia, including but not limited to training and licensing of all members, and the documentation of all such military arms.