States with a heavier dose of firearm laws tend to have the lowest rates of gun deaths, according to a study released Wednesday by Boston-based researchers who argue their findings show "there is a role" in America for more rigid gun-control legislation.

"It seems pretty clear: If you want to know which of the states have the lowest gun-mortality rates just look for those with the greatest number of gun laws," said Dr. Eric W. Fleegler of Boston Children's Hospital who, with colleagues, analyzed firearm-related deaths reported to the Centers for Disease Control and Prevention from 2007 through 2010.

By scoring individual states simply by the sheer volume of gun laws they have on the books, the researchers noted that in states with the highest number of firearms measures, their rate of gun deaths is collectively 42 percent lower when compared to states that have passed the fewest number of gun rules. The study was published online in the journal JAMA Internal Medicine.

As proof, Fleegler pointed to the firearm-fatality rates in law-laden states such as Massachusetts (where there were 3.4 gun deaths per 100,000 individuals), New Jersey (4.9 per 100,000) and Connecticut (5.1 per 100,000). In states with sparser firearms laws, researchers reported that gun-mortality rates were higher: Louisiana (18.0 per 100,000), Alaska (17.5 per 100,000) and Arizona (13.6 per 100,000). 

In Arizona -- just as the new study was released -- former Rep. Gabrielle Giffords returned Wednesday to the grocery store where she was shot and urged Congress to expand background checks for gun purchases. She told the gathered crowd and U.S. lawmakers to: "Be bold. Be courageous. Please support background checks." 

On Thursday, the Senate Judiciary Committee is expected to vote on a bill that would stiffen penalties for people who purchase guns illegally for others, and to make gun trafficking a felony. 

Fleegler and his team openly acknowledged they could not prove a definitive "cause-and-effect" link between tighter laws and a lower risk of gun-caused homicides or gun-related suicides. But ahead of the expected Senate vote, the researchers said they did determine this:

In those states that have the most firearm laws, those states also have the lowest rates of household-firearm ownership.

"And states that have the lowest gun-ownership rates also have the lowest gun-mortality rates," Fleegler said. "So states that try to have gun laws that are meant to be meaningful, they seem to be able to actually have an impact. That’s an important thing to learn from."

The findings were quickly challenged by two critics,  a top gun-rights advocate and a leading expert on the nexus of public health and gun policy, who each questioned the merits of the Boston findings and the rigor of the science behind the study.

It sounds to me like some sort of sleight of hand from a political sense," said Dave Workman, senior editor at Gun Week magazine and director of communications for the Citizens Committee for the Right to Keep and Bear Arms, in Bellevue, Wash.

"If they are dancing around this cause and effect, I'm not sure that the public should warm up to that kind of a conclusion because it really doesn't conclude it, it only suggests or intimates something," said Workman, who served three terms on the National Rifle Association board of directors.

"It's presumably the result they wanted to get in order to have the public believe something. Is that fair? Is that good science? Is that good research? I don't know." 

Workman further argued that in states or jurisdictions where gun laws "make it difficult for law-abiding citizens" to buy firearms through legal channels, "that does not necessarily translate to lower fatalities."

"And, as proof," he added, "I give you the city of Chicago." 

In an accompanying commentary, Dr. Garen J. Wintemute of the University of California, Davis, Sacramento, wrote that the paper's conclusion "would be an important finding — if it were robust and if its meaning were clear."

Ultimately, Wintemute wrote, the new study provides no insights on the key questions facing Congress: "Do the (gun) laws work, or not? If so, which ones?"

"Correlation does not imply causation," Wintemute said in a phone interview. "The plain English way of saying this is: Just because two things exist at the same time, that does not mean one thing caused the other. That's what's being implied here. All they counted in that analysis was the number of laws in each state, not which laws. There's no information in this study on the specifics of the (state) laws and whether they were enforced or not."

"So in a sense, the only conclusion you could draw would be: Pass more more laws but it doesn't matter which ones or what they're intended to do," Wintemute said. "That's just silly." 

Fleegler's study was not related to a recent executive order by President Barack Obama lifting a ban on gun violence research funded by federal agencies such as the CDC. Fleegler said he used public data at no cost to conduct his analysis. 

Wintemute said the study actually underscores the need for well-funded research into the effects of gun violence on public health. 

"Until we revitalize firearm violence research, studies using available data will be the best we have. They are not good enough."

Related stories:

• Guns in America: The weapon of choice for criminals, but also a deterrent?
• Obama plan eases freeze on gun research

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