A federal rule requiring background checks doesn't apply to some of those doing business online and at gun shows, like this one put on by the National Rifle Association in April in St. Louis. Changing that exception is one idea that has been floated to the president. Jeff Roberson/AP hide caption
Enrique Marquez is pictured in a courtroom sketch on Dec. 17, the day he was charged with conspiring to provide material support to terrorists. He was indicted on this and other charges on Wednesday. Bill Robles/AP hide caption
Smoke rises from ISIS positions following a U.S.-led coalition airstrike in the Huz neighborhood in downtown Ramadi, Iraq, on Saturday. Osama Sami/AP hide caption
Members of the Los Angeles Police Department's elite Metropolitan Division participate in a simulation of a Paris-style coordinated attack. The team was tested on response time to converge on this site. Martin Kaste/NPR hide caption
Shawn Alexander and Ashley Jimenez visit a madrassa in the Los Angeles area. The two police officers are part of the Los Angeles Police Department's counterterrorism bureau, which is focused on fostering community engagement. Martin Kaste/NPR hide caption
Democratic presidential candidate Hillary Clinton speaks about her counterterrorism strategy during a speech at the University of Minnesota in Minneapolis on Tuesday. Charlie Neibergall/AP hide caption
After recent terrorist attacks, social media companies are under pressure to do more to stop messaging from terrorist groups. Patrick George/Ikon Images/Getty Images hide caption
A person walks to Friday Prayer at the Omar Mosque in Paterson, N.J. in 2012. With Islamophobia surging in recent weeks, many Muslims in Paterson say they are feeling frightened and unsettled. Spencer Platt/Getty Images hide caption
Connecticut Gov. Dannel Malloy listens to a memorial service for the victims of the Sandy Hook Elementary School shooting in December 2012. Jessica Hill/AP hide caption
Airmen use a ground-control station cockpit to control remotely piloted aircraft Nov. 17 during a training mission at Creech Air Force Base in Indian Springs, Nev. The Pentagon plans to remotely piloted aircraft flights by as much as 50 percent in the next few years to meet increased needs for surveillance, reconnaissance and lethal airstrikes around the world. Isaac Brekken/Getty Images hide caption
Russell Moore, president of the Southern Baptist Convention's Ethics and Religious Liberty Commission, said Donald Trump's "reckless, demagogic rhetoric" was an affront to religious freedom. Mark Humphrey/AP hide caption
Ted Cruz visited NPR headquarters on Tuesday to talk with Steve Inskeep about his plans for protecting the U.S. from terrorist attacks and his views on climate change. Ariel Zambelich/NPR hide caption