While federal law prohibits dealers from selling new vehicles with unfixed recalls, there is no law that prevents used cars with similar problems from being sold.
Sen. Richard Blumenthal (D-CT) and Sen. Edward Markey (D-MA) reintroduced the Used Car Safety Recall Repair Act in June 2019 to close that safety loophole.
The bill is currently being reviewed by the Committee on Commerce, Science, and Transportation. The senators had previously pushed for similar legislation in 2015 but the proposal received pushback from automobile dealers and ultimately wasn’t signed into law.
There are, however, state consumer protection laws that could be applied towards dealers.