WASHINGTON — The Obama administration said Thursday it has closed a loophole in the gun laws that allowed the acquisition of machine guns and similar weapons and has banned U.S. military-style firearms that were sent overseas from returning to this country.

The announcement of President Obama’s two new executive actions came as Vice President Joe Biden swore in the new head of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), the first Senate-confirmed director in the agency’s history. Biden pledged that the Obama administration will not give up its effort for more gun control despite congressional inaction after the massacre at a Connecticut elementary school last year.

“The president and I remain committed to getting these things done,” Biden said at the White House ceremony installing B. Todd Jones as the ATF’s first permanent director in seven years. “If Congress won’t act, we’ll fight for a new Congress. It’s that simple. But we’re going to get this done.”

In the past, individuals seeking to avoid personal background checks for machine guns and short-barreled shotguns have claimed they were “trusts or corporations.” But a new ATF regulation will close that loophole and require them to pass background checks. Last year, the ATF said, it received more than 39,000 requests for transfers of these firearms to trusts and corporations in ruses to skirt the checks.

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“It’s a very artful dodge,” Biden said.

The other executive action was aimed at keeping U.S. military weapons sold to foreign governments from being reimported to individuals in this country. Since 2005, the U.S. government has authorized requests to reimport more than 250,000 of these firearms. Under the new rule, only firearms reimported for museums and other such exceptions would be allowed.

“We’re ending the practice,” said the vice president, who after the shooting at the Sandy Hook Elementary School in Newtown, Conn., was named to oversee an effort to come up with gun-control related mental-health measures.