The Federal Bureau of Alcohol, Tobacco, and Firearms (ATF) is the federal agency responsible for enforcing gun laws. Most of the US laws regulating firearm sales are contained in the Code of Federal Regulations, Part 478 - Commerce in Firearms and Ammunition.
The ATF has a comprehensive site containing information about various federal and state laws regulating firearms:
- ATF Home page:
http://www.atf.gov - ATF Frequently Asked Questions
http://www.atf.gov/questions-and-answers/firearms-faqs - ATF Firearms Division Main Page:
http://www.atf.gov/content/Firearms/firearms-industry - ATF Frequently Asked Questions - Unlicensed Persons
http://www.atf.gov/content/firearms-frequently-asked-questions-unlicensed-persons - NRA Guide to State-by-State Laws
https://www.nraila.org/gun-laws/state-gun-laws/
For California residents, handguns must pass a 'drop test' to be legal to bring into or sell in the state of California. Visit the CA DOJ Certification List page.
The ATF Learning Theatre (https://www.youtube.com/playlist?list=PL3CF3B643FCBDACFE) shows several examples of how to sell and ship firearms and the laws you must follow, including rules about:
- Long Gun Transactions
- Hand Gun Sales
- Multiple Firearm Transactions
- Straw Purchases
- Out of State Transactions