I’m going to suggest this is likely a case of correlation not equaling causation, but expect the Brady’s to be touting this high and low. They mention 17 states as having state and local checks, but according to the DOJ, only 13 states have local POCs for firearms background checks, so the sample size is rather small. States which have local POCs:
- California
- Colorado
- Connecticut
- Florida
- Hawaii
- Illinois
- Nevada
- New Jersey
- Oregon
- Pennsylvania
- Tennessee
- Utah
- Virginia
Of course, that nearly 2/3rds of the states are there are generally pro-gun is something to consider. Another thing to consider is there’s a class of state that has state checks for pistols, and uses NICS for long guns. Maryland falls into that category. Since most crimes and suicides involving a gun involve a handgun, I think a study should include those as well. I’m not sure where they are getting 17 states from, and only 21 states relying on federal checks, since the DOJ states differ, and say it’s 28 states. I haven’t read the study though.