In light of the mass shooting in San Bernardino, California, and the speculation surrounding the shooters' connection to terrorist groups, many people—including President Barack Obama—are revisiting a loophole that allows suspected terrorists on the nation's No-Fly List to purchase guns and explosives.

Related: These Gun Laws Could Help Stop Mass Shootings

If you're on the No-Fly List, you can't get on planes, but you can purchase guns.

Kim Seng, Flickr - flickr.com

Under the current rules for background checks, people on the No-Fly List are legally able to purchase guns and explosives, according to the Guardian. The No-Fly List is what it sounds like: a list of people who are not permitted to board commercial airlines into or out of the United States. While not every person on the list got there because they are a suspected terrorist — people have made the list for other criminal issues — the Justice Department adds people of whom there is a “reasonable suspicion” that they could be dangerous to the United States.

"Right now, people on the No-Fly list can walk into a store and buy a gun. That is insane. If you're too dangerous to board a plane, you're too dangerous, by definition, to buy a gun," the president said in his weekly address. "And so I'm calling on Congress to close this loophole, now. We may not be able to prevent every tragedy, but — at a bare minimum — we shouldn't be making it so easy for potential terrorists or criminals to get their hands on a gun that they could use against Americans."

Republicans are opposed to the change, citing Due Process rights.

AP/Evan Vucci - apimages.com

Republicans in Congress are opposed to this change, arguing that banning gun purchases by individuals on the No-Fly List could be a violation of constitutional rights. Speaker of the House Paul Ryan (R-Ohio) said that because names are added without formal due process, this change could deprive innocent people of their Second Amendment right to bear arms. Many, including the ACLU, have criticized the No-Fly List for this reason, citing instances where innocent people were added and barred from air travel without any explanation. (The ACLU has challenged the legality of the process.)

Republican presidential candidate Jeb Bush said the same thing on Saturday, indicating that he would be open to a ban if the No-Fly List was tightly limited to individuals who were subject to active investigation for terrorism.

"You would have to narrow it down to the point where it was clearly, there’s an active investigation of something like that,” Bush said on Fox News.

Related: Here's Why Doctors Can't Call Gun Violence a Public Health Issue

Three people on the No-Fly List have purchased guns.

According to the Guardian, three people on the U.S. No-Fly List have legally purchased guns and explosives, passing a federal background check. The three individuals were registered for explosive checks between 2004 and 2014 through the National Instant Background Check System (NICS) and were each granted access to buy weapons.

As ATTN: has previously reported, not all states have laws that make it difficult for potential terrorists to purchase guns. Only 13 states currently have expanded background checks, and only 8 states have implemented laws that ban large-capacity magazines.

Federal Bureau of Investigation - fbi.gov

Al-Qaeda has encouraged its supporters to take advantage of American gun laws.

Many are concerned that these seemingly lax gun laws could play into the hands of terror groups and their members and supporters.

Related: ISIS Just Responded to the San Bernardino Shooting with a Chilling Message

In a video recorded before his death, American Al-Qaeda leader Adam Gadahn produced a video urging the group's members to take advantage of America's gun laws, Slate reports.

"In the West, you’ve got a lot at your disposal. Let’s take America for example. America is absolutely awash with easily obtainable firearms," he said. "You can go down to a gun show at the local convention center and come away with a fully automatic assault rifle without a background check and most likely without having to show an identification card. So what are you waiting for?"