TLDR: In 2016, Zen Magnets won a court case which allowed them to resume selling their 5mm magnet sets again. In 2020, the CPSC appealed to overturn this decision and were successful, barring Zen Magnets from selling 5mm magnet sets ever again.
High powered magnet sets have been illegal to sell as children's toys since 2009. Unsatisfied that this ban would keep magnets out of the hands of children, the CPSC began a campaign in 2012 to completely rid the market of 5mm magnet sphere sets. They sued Buckyballs and Zen Magnets, and began work on a rule that would ban both companies' products (or any magnet sets of similar strength). Zen Magnets survived, though Buckyballs was dissolved by 2014.
In 2014, the CPSC finalized their rule which banned magnet sets such as Zen Magnets/Neoballs for any age group. Zen Magnets immediately appealed this decision in federal court. In 2016, the judge finally ruled in favor of Zen Magnets, allowing them to be able to import/sell/distribute 5mm magnet sphere sets for adults (ages 14+).
However, this decision also opened up the market for anyone to sell. With no regulations on packaging or labeling, the market was soon flooded with generic magnets boasting no warnings or age restrictions. Zen Magnets appealed to the CPSC to define regulations and standards for magnet sets, they refused. While magnet sets were still illegal to sell as children's toys during this time, the CPSC appeared to not enforce this rule for the next 4 years. Amazon.com, whose listing rules explicitly prohibits 5mm magnet sets, was overflowing with unregulated magnet sets listed as kids' toys and even developmental baby toys. Unsurprisingly, reports of magnet ingestions rose significantly between 2016 and 2020.
In 2020 the CPSC appealed the decision which made magnet sets legal to sell again, to have it overturned. The CPSC successfully appealed the decision and Zen Magnets was no longer able to import/sell/distribute 5mm magnet sphere sets. As of January 2021, this decision only stops the Zen Magnets company from selling magnet sets, though the CPSC will surely reenact their nationwide all ages magnet ban soon enough.