# Extreme risk protection orders and firearm violence: a synthetic control analysis

## TL;DR

This study examines how different versions of Extreme Risk Protection Orders (ERPOs) affect firearm violence in various U.S. states.

## Contribution

The study uses a synthetic control approach to evaluate the effectiveness of ERPO policies in reducing firearm violence.

## Key findings

- ERPO policies in Rhode Island and Massachusetts were associated with significant reductions in nonfatal firearm assault.
- ERPO policies in Florida, Oregon, Vermont, and Washington did not show significant changes in firearm violence incidents.
- California, Delaware, Illinois, and Maryland results were uninterpretable due to poor pre-period fit.

## Abstract

Extreme Risk Protection Orders (ERPOs) are an evidence-based provision to prevent firearm violence present in 21 states, and Washington D.C. as of 2024. Examining the potential of varied ERPO versions to prevent fatal and nonfatal forms of firearm violence is crucial for shaping effective policy creation and enactment.

We use a synthetic control approach to estimate how varied ERPO versions impact firearm violence incidents resulting in injury and/or death per the Gun Violence Archive between 2014 and 2021. Our ‘treated’ state cohort (California, Delaware, Florida, Illinois, Massachusetts, Maryland, Oregon, Rhode Island, Vermont, and Washington) had ERPO effective dates after 2015 and before 2019, and experienced a statistically significant increase in petitions relative to the petition volume (zero) before ERPO implementation.

Significant reductions in state-month firearm violence rates were associated with ERPO policies in Rhode Island and Massachusetts (due largely to reductions in nonfatal firearm assault). Florida’s, Oregon’s, Vermont’s, and Washington’s ERPO policies were not associated with changes in firearm violence incidents. Poor pre-period fit made California, Delaware, Illinois, and Maryland results uninterpretable.

We conclude not all ERPO policies are created or implemented equally. Under certain enactment and implementation conditions, ERPO policies may protect against nonfatal firearm assault incidents in particular. Increasing effect sizes over time may suggest state capacity for implementing ERPOs effectively is improving, however, effect size magnitudes also indicate factors other than ERPO policies may be contributing to observed declines.

The online version contains supplementary material available at 10.1186/s40621-026-00663-8.