Others probably have better info, but I thought it the law addressed possession of unserialized firearms in the state.
Edit: Here is at least some of the language from a press article:
"The law that Raimondo signed in June prohibits possessing, making or selling guns that lack a unique serial number engraved on the frame or receiver, which is the main part of a gun that holds the rest together."
Biden's executive action requires more parts of a homemade gun to have a serial number.
www.providencejournal.com