This commentary is a joint publication of Foreign Policy In Focus and the Washington Office on Latin America.

Since the horrific shooting at Sandy Hook Elementary School, the movement to prevent gun violence in the United States has gained new resolve and new energy.

Even as Congress has defied public opinion on common-sense measures to reduce gun violence—such as expanding the background check system and enacting stiffer penalties for gun traffickers—legislatures in states like Connecticut, Colorado, New York, and Maryland have forged key reforms at the state level.

Of course, there have been setbacks as well: some states have moved to weaken gun laws, and two state legislators in Colorado were recently recalled after supporting reforms. The National Rifle Association remains a very powerful force.

For his part, President Barack Obama has made it clear that he is not going to wait for Congress to act. After the Newtown shooting, he announced 23 executive orders to prevent gun violence, including measures to strengthen the background check system. After Congress’ failure to pass legislation, President Obama signed further executive orders to restrict military surplus guns like the M-1 assault rifle and close a background check loophole.

The Washington Navy Yard shooting in September 2013 spurred Obama to again turn to Congress. “Congress is going to have to act,” he said. “We’ve put in place every executive action that I proposed right after Newtown happened. So I’ve taken steps that are within my control. The next phase now is for Congress to go ahead and move.”

Congress should indeed take action. But there’s at least one problem that Obama can address without waiting for Congress: the importation of assault weapons.

We often hear of U.S. guns turning up at crimes scenes abroad. But we rarely hear about how so many foreign-made guns find their way to the United States. Currently, the U.S. market is flooded with imported firearms from Brazil, Austria, Germany, and many other countries.

Imported weapons also play a significant role in cross-border firearms trafficking, with guns like the Romanian-manufactured WASR-10 becoming increasingly coveted by traffickers. These guns are helping to fuel violence in Mexico, where drug-related violence continues to devastate communities. Seventy percent of all guns recovered in Mexico and submitted for tracing come from the United States, and a significant portion of those were first imported to the United States from elsewhere.

Imported guns are popular among traffickers because they are often much cheaper than domestic models. While a U.S.-manufactured AR-15 assault rifle can cost up to $1,300, a foreign-made AK-47 can be purchased for as little as $300. Imported firearms are also more dangerous, as they can easily be converted into fully automatic weapons. They are used by criminals in cities throughout the United States, and have been involved in a number of mass shootings across the country, from Omaha, Nebraska to Carson City, Nevada and St. Louis, Missouri.

Under the Gun Control Act of 1968, the president has the authority to prohibit companies from importing guns that are not “for sporting purposes.” Two presidents, one Republican and one Democrat, have aggressively used this authority. President George H. W. Bush declared a permanent ban on assault weapons in 1989, and President Bill Clinton strengthened the ban in 1998 by prohibiting the importation of 50 types of assault weapons. This ban remains in place today.

During the George W. Bush administration, however, enforcement of the ban became lax. For reasons that are still not entirely clear, U.S. companies such as Century International have easily been able to exploit loopholes in the ban. (It certainly has not helped that, until summer 2013, the ATF lacked a permanent director). In many cases, companies have succeeded in having many assault rifles classified as “for sporting purposes,” which exempts them from the ban. They have also imported the weapons in parts and assembled them in the United States.

As a result, the U.S. market is awash with cheap imported weapons. The volume of importation varies from year to year. But in 2011 alone, U.S. companies imported more than 3 million firearms, according to the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF).

That year, 53 members of Congress called on President Obama to take action to stop the importation of assault weapons. While the president’s 2013 directive to prohibit the importation of military surplus weapons was a positive step, it only dealt with guns that are produced in the United States, sold to foreign militaries, and then re-imported. It did not address the larger problem of commercially imported assault weapons.

President Obama can stop the importation of these dangerous weapons by ordering the ATF to issue a new rule that would close the loopholes and fully enforce the ban. He should issue the order without delay.

Clay Boggs is a program officer at the Washington Office on Latin America (WOLA).