From Bearing Arms:

The Biden Administration issued guidance in 2022 to make these unfinished parts subjected to the same regulation as completed firearms.

A new rule in April 2022 required gun manufacturers to complete background checks and add serial numbers to parts.

Despite, the crackdown, the ABC11 I-Team purchased parts for a popular name-brand handgun online after the rule went into effect and received parts without serial numbers and the site did not conduct a background check.