Flexing its political muscle on Capitol Hill, the NRA successfully pushed for legislation that effectively ended Rosenberg's program.

To underscore its point, Congress -- in a move led by Jay Dickey, a former gun-rights advocate and Republican legislator from Arkansas -- added this language to the agency's appropriation: "None of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control."

At the time, critics in Congress accused the researchers of pursuing an anti-gun agenda and said the CDC's work was redundant.

The provision remains in place today.

The language created what Teret called "a chilling effect" for nearly all gun-related work at the CDC. Though the agency continues to track gun deaths and injuries, it does little work on how to prevent them.

Many years later, the National Institutes of Health funded a similar study that triggered the same lightning-bolt response.

In 2009, the NIH study concluded that a person carrying a gun was nearly 4.5 times more likely to be shot in an assault than someone who is unarmed.

Two years later, Congress added the same restrictive language it had imposed on the CDC to all agencies of the Department of Health and Human Services, including the NIH.

Today, the NRA maintains its position that government research into gun violence is not necessary.

"What works to reduce gun violence is to make sure that criminals are prosecuted and those who have been found to be a danger to themselves or others don't have access to firearms," the NRA's Arulanandam said, "not to carry out more studies."

Unanswered questions

So why are government studies on gun violence necessary?

Rosenberg, who left the CDC in 1999, explained that many of the questions that his group was seeking to answer remain open.

For example, he said, it's not clear whether registering and licensing firearms lowers gun violence; whether allowing people to carry concealed weapons increases or lowers the risk of gun deaths; or how letting people carry weapons in places such as shopping malls or schools or bars or parks affects the number of deaths.

"These are very big questions that we need to know the answer to," said Rosenberg, who is now president and CEO of The Task Force for Global Health.

There are other private agencies and even partly federally funded programs that have researched these issues.

But none was as far-reaching as what Rosenberg's program did in the 1990s.

The CDC's website still keeps track of the toll of gun violence -- or, as the CDC sometimes calls it, "lethal means." Yet, the federal agency does little of the epidemiological research it once did that might offer guidance to lawmakers.

Now that gun violence has been thrust into the forefront of issues on Capitol Hill after last month's mass shooting at a Newtown, Connecticut, elementary school, the focus has turned to the medical community's role in the debate.

Last week, The Washington Post reported on a little-known provision added to the 2010 Affordable Care Act -- better known as Obamacare -- limiting what doctors can ask their patients about firearms in the home.