GUNS WERE USED to commit two-thirds of the 97 murders in Prince George’s County last year. So the county council is considering a new strategy to reduce violent shootings: put anyone convicted of a range of gun offenses in Prince George’s on a special police registry.

Figuring out just how much specific policies would discourage illegal gun use is difficult, not least because the National Rifle Association (NRA) has repeatedly convinced Congress to pull funding from federal studies on gun violence. But any reasonable approach to stigmatize the possession and use of illegal firearms is worth trying. And this strikes us as very reasonable.

A gun registry would target only lawbreakers, and a subset of them that is particularly prone to commit violent crimes. It would not be a brand for life. For three or five years, depending on the crime, the offenders would have to update their entries every time they moved, and they would have to visit the police every six months. That would generate useful information for front-line officers who have to know the neighborhoods they patrol and detectives investigating major crimes.

A few officers would also regularly visit those on the county’s registry — an added deterrent against reoffending. The threat of years of scrutiny might even deter first-time gun offenses. Visiting officers, though, would not conduct searches, limiting concerns about heavy-handed police intrusion.

Gun offenders are most likely to reoffend during the first year following their release, says District Police Chief Cathy L. Lanier. Part of the logic of Washington’s registry system, enacted in 2009, is that it extends a certain amount of supervision past that dangerous first year.

New York City was the first to experiment with a gun offender registry, establishing one in 2006. Since, the murder rate has dropped, and the city is on course to have its lowest annual number of homicides since it began keeping records in 1963. Ms. Lanier also describes impressive results in the District. But it is hard to isolate the effects of the registry from the “symphony” of tough anti-gun policies, a New York City spokesman admits. Baltimore, which followed New York’s lead in 2007, touts a lower rate of repeat crime among those on its gun registry than the national average for gun offenders, but that could also be for other reasons. Such uncertainty, though, is not evidence that these registries are ineffective, as the NRA claims.

It is NRA lobbying that encourages uncertainty on gun policy. The federal government should be helping states to establish the efficacy of gun-offender registries and other policies by running national studies on them. Instead, Congress in 1996 cut funds from the Centers for Disease Control and Prevention to study gun violence, and last year the GOP-controlled House did the same for the National Institutes of Health.

Prince George’s County, Washington, New York City and Baltimore should continue to experiment with new tools to reduce gun deaths, and Congress should stop treating facts as illegitimate threats to gun rights.