The question people often ask is what does that mean?

"The right of the people to keep and bear arms shall not be infringed" gives the people the right to be armed for their personal self-defense," Dr. Joyce Malcolm, who teaches constitutional law at George Mason University School of Law, explained.

Insurance Policy for Freedom

It also serves as an insurance policy for liberty.

"It's the idea that out of 300 million Americans about 90 million own firearms," Ken Klukowski, director of the Center for Religious Liberty at the Family Research Council, said.

"When you have 90 million firearms out there, that mere fact is a deterrent to any future head of state that this is a fight he would not want to pick," he added.

The fight Britain picked with American colonists sparked the Bill of Rights. Americans attached the list to the Constitution after the British crown tried to take them away.

"There are plenty of constitutions in the world that have wonderful lists of rights and the people don't enjoy any of them. So the Second Amendment was meant to be a protection," Malcolm said.

District of Columbia vs. Heller

Still, as recently as 2008, there were questions about whether the Second Amendment guaranteed not just a militia's right, but an individual's right to bear arms.

The U.S. Supreme Court settled the matter in http://www.supremecourt.gov/opinions/07pdf/07-290.pdf - District of Columbia vs. Heller .

"The Second Amendment protects an individual right to possess a firearm unconnected with service in a militia and to use that arm for traditionally lawful purposes, such as self-defense within the home," the High Court ruled.

"When someone breaks in with a weapon you have not just the right, but the obligation to protect not just your life, but the lives of the little ones that have been entrusted to you," Klukowski explained.

The court also held that the Second Amendment isn't unlimited, specifically noting:

• Longstanding prohibitions of firearms by felons and the mentally ill
• Laws forbidding the carrying of firearms in sensitive places such as schools
• The regulation of the commercial sale of arms

Assault Weapons Ban

President Obama and some members of Congress want to ban the sale of so-called assault rifles.

However, the Heller decision made it clear that popular firearms can't be banned. Many would argue that ruling covers assault rifles since they're popular among Americans for both self-defense and hunting.

"Faithful adherence to the original meaning of the Constitution is the cornerstone to protecting individual and family liberty in every regard, including the Second Amendment," Klukowski said.

Crimes committed with guns, like the tragedy at Sandy Hook Elementary School in Newtown, Conn., periodically shift public opinion on the Second Amendment.

Still, Malcolm said it's just as relevant today as it was in 1791.

"There's this sort of root, gut feeling in the American public that they have a right to be armed," she said.