Firearms law is a layered system in which federal rules set a floor, state rules vary enormously above it, and a person can be entirely lawful in one place and committing a felony an hour's drive away. This article explains who is prohibited from possessing a firearm and why the categories are broader than most people expect, including the misdemeanor and restraining order provisions that surprise people who have never been convicted of a felony. It covers how purchases actually work, what a straw purchase is and why it is prosecuted aggressively, and the interstate transport safe harbor that protects travelers who follow it precisely. Separate parts address the National Firearms Act items that require registration, the constitutional framework after recent decisions, and the routes by which lost firearm rights can sometimes be restored. Examples run throughout. The article is written for gun owners, people facing charges, and lawyers new to the area.