MI SB1149

Prohibits manufacturing, assembling, importing, purchasing, selling, or transferring firearms and frames/receivers without valid serial numbers, with exceptions for antique firearms, law enforcement, and licensed entities.

Bans the sale and importation of "ghost gun precursors" (unserialized frames or receivers) immediately and requires possession of such items to cease 18 months after the law's effective date.

Requires unlicensed manufacturers of firearms to obtain serial numbers within 10 days, notify the state police director, and provide identifying information; those making more than 5 firearms annually or using 3D printers/CNC machines must obtain a manufacturing license.

Prohibits the manufacture or assembly of undetectable firearms (those made entirely of nonmetal or undetectable by metal detectors and X-ray machines) and prohibits facilitating manufacture by prohibited persons.

Establishes penalties of up to 1 year imprisonment and $5,000 fine for first offense; up to 5 years imprisonment and $10,000 fine for subsequent offenses; includes exemptions for individuals moving into the state (90-day compliance window) and those transporting unserialized firearms to licensed gunsmiths for serialization.