Bad news for the NRA: a new study shows that if a state requires a license before a gun can be purchased, there are 14 percent less gun-related murders in big cities.

Getting a gun does not require a license at the federal level, but a number of states have what's called permit-to-purchase licensing laws, which require a background check done by the local or federal police.

The study—conducted by Johns Hopkins Bloomberg School of Public Health—showed that states with gun licensing laws had a significant reduction in firearm homicides in large urban areas.

Generally, you'd apply for the license directly through law enforcement. And a number of the states also require fingerprinting as part of the licensing process.

The researchers also found that states that only require comprehensive background checks (CBCs) actually have a 16 percent higher rate of firearm related homicides versus those with permit-to-purchase laws. In these situations, the background check is done by the gun seller, and doesn't always go through the local law enforcement.

This study shows that CBCs are important in gun control, but may not be enough on their own say the researchers. Licensing laws take more time and are more thorough, and CBCs are often based on databases that are incomplete.

The study also looked at 'Right to Carry' and 'Stand Your Ground' laws. The former makes it easier to carry a concealed weapon, and the latter gives gun owners more protection if they use potentially deadly force against intruders. In both cases, states that had these laws saw more gun deaths in large urban centers