MI SB0331

Prohibits manufacturing, assembling, importing, purchasing, selling, or possessing firearms without valid serial numbers, with possession ban taking effect 18 months after the law's effective date

Bans the sale, transfer, import, or possession of "ghost gun precursors" (unserialized frames or receivers) and undetectable firearms that cannot be identified by metal detectors or X-ray machines

Requires individuals who manufacture or assemble firearms without a federal license to have them serialized within 10 days and notify the Michigan State Police director with identifying information

Mandates a federal firearms manufacturing license for anyone making firearms for profit, producing more than 5 firearms per year for personal use, or using 3D printers or CNC milling machines to create firearms

First offense violations are misdemeanors punishable by up to 1 year imprisonment and/or $5,000 fine; second or subsequent offenses are felonies with up to 5 years imprisonment and/or $10,000 fine