Persons with mental illness or substance abuse have been perceived by the public to pose an increased risk of violence to themselves and others. As a result, federal and state laws have restricted the right of certain categories of persons with mental illness or substance abuse to possess, register, license, retain, or carry a firearm. Clinicians should be familiar with the specific firearm statutes of their own states, which describe the disqualifying mental health/substance abuse history and the role and responsibility of the psychiatrist in the process. State statutes vary widely in terms of the definitions of, and reporting requirements relating to, prohibited persons with mental illness or substance abuse. States also vary in the duration of the prohibition and in the timing of the appeals process. Some of the statutes have specific provisions for the removal of a firearm when a prohibited person is identified. States may maintain a mental health database that is used to determine firearm eligibility and may forward information to the National Instant Criminal Background Check System. The National Instant Criminal Background Check System Improvement Amendments Act of 2007 will likely increase the number of persons identified as belonging to the prohibited class.