Congress’s omnibus bill is taking a very limited step toward letting the Centers for Disease Control and Prevention (CDC) study gun violence. But it’s an open question just how much of an effect the spending deal will have.

For years the CDC has interpreted a law, called the Dickey Amendment, as a ban on studying gun violence. The new budget deal clarifies that the amendment doesn’t prevent them from doing this work, potentially allowing the CDC to research gun violence and its causes.

The amendment technically barred the CDC from spending any money “to advocate or promote gun control.” It was enacted following outcry by groups like the National Rifle Association over studies in the 1990s that showed — and have since been supported by further research — that the presence of guns actually increases the risk of injuries and deaths in homes, contrary to claims that they make homes safer.

This context led the CDC to worry about what could be construed as advocating for gun control, given that studies that simply showed observable risks to gun ownership led to such backlash.

As a result, CDC research funding for gun violence fell by 96 percent between 1996 and 2012, according to Everytown for Gun Safety, which backs gun control. “Major public research funding for gun violence prevention is estimated at $2 million annually,” the group found. “By contrast, in 2011, the National Institutes of Health devoted $21 million to the study of headaches.”

Public health and gun policy researchers have long advocated for change. After finishing a two-year review of the empirical evidence, RAND Corporation researchers concluded that the dearth of good studies essentially leaves the public blind — and creates an environment in which it’s difficult to suss out what specific policies would work best to tamp down on gun violence.

“The studies that have been done often reach opposite conclusions to each other,” Andrew Morral, the head of RAND’s gun policy initiative, previously told me. The lack of thorough research, he added, “creates this kind of fact-free environment in which people can cherry-pick any study that happens to support what their priors are on the effects of the law.”

There has been some good research. The RAND review, for instance, suggested that some gun control measures — background checks, child access prevention laws, minimum age requirements, and prohibitions associated with mental illness — are linked to reductions in injuries and deaths, based on the most rigorous studies in the US so far.

But Morral cautioned that the evidence is far from ideal, previously telling me, “There’s been so little research that we’re really at the mercy of a few studies.”

Again, Congress’s budget deal doesn’t eliminate the Dickey Amendment; it only clarifies some parameters. This kind of approach has failed before: A previous executive order by President Barack Obama to attempt to boost the study of gun violence without getting rid of the Dickey Amendment didn’t lead to significant new research.

But it’s at least a potential start.

For more on the state of gun violence research, read Vox’s explainer of the RAND report.