From the Associated Press:

One new policy will end a government practice that lets military weapons, sold or donated by the U.S. to allies, be reimported into the U.S. by private entities, where some may end up on the streets. The White House said the U.S. has approved 250,000 of those guns to be reimported since 2005; under the new policy, only museums and a few other entities like the government will be eligible to reimport military-grade firearms.

The Obama administration is also proposing a federal rule to stop those who would be ineligible to pass a background check from skirting the law by registering certain guns, like machine guns and short-barreled shotguns, to a corporation or trust. The new rule would require people associated with those entities, like beneficiaries and trustees, to undergo the same type of fingerprint-based background checks as individuals if they want to register those types of guns.