https://www.cnn.com/2022/06/29/us/ghost-gun-lawsuit-new-york-city/index.html

Authorities in New York filed lawsuits against 10 companies selling parts for so-called ghost guns, in an effort to hold distributors accountable for the proliferation of mail-order components used to make untraceable guns that lead to shootings.

The lawsuits, invoking a newly enacted state "public nuisance" law, hit companies on multiple fronts, including one from the New York Attorney General Letitia James field against 10 distributors in state supreme court and another by the New York City Law Department against five of the same companies, filed in federal court in Manhattan.

https://www.federalregister.gov/documents/2022/04/26/2022-08026/definition-of-frame-or-receiver-and-identification-of-firearms
This rule is effective August 24, 2022.
In the past few years, some courts have treated the regulatory definition of “firearm frame or receiver” as inflexible when applied to the lower portion of the AR-15-type rifle, one of the most popular firearms in the United States. If broadly followed, that result could mean that as many as 90 percent of all firearms (i.e., with split frames or receivers, or striker-fired) in the United States would not have any frame or receiver subject to regulation. Furthermore, technological advances have also made it easier for companies to sell firearm parts kits, standalone frame or receiver parts, and easy-to-complete frames or receivers to unlicensed persons, without maintaining any records or conducting a background check. These parts kits, standalone frame or receiver parts, or partially complete frames or receivers enable individuals to make firearms quickly and easily. Such privately made firearms (“PMFs”), when made for personal use, are not required by the GCA to have a serial number placed on the frame or receiver, making it difficult for law enforcement to determine where, by whom, or when they were manufactured, and to whom they were sold or otherwise transferred. Because of the difficulty with tracing illegally sold or distributed PMFs, those firearms are also commonly referred to as “ghost guns.”