United States v. Article Consisting of 50,000 Cardboard Boxes More or Less, Each Containing One Pair of Clacker Balls, 413 F. Supp. 1281 (E.D. Wisc. 1976), is a 1976 United States District Court for the Eastern District of Wisconsin decision regarding a requested order from the United States government to seize and destroy a shipment of approximately 50,000 sets of clacker balls under the Federal Hazardous Substances Act because children could hit themselves with the balls.
There is no “link to what they were in the Wikipedia page”, I had looked for that before I commented. If you’re referring to a specific reference it would be great if you could share which one, as none of them have a title relating to “what those clacker balls were”.
https://en.wikipedia.org/wiki/Clackers?wprov=sfla1
If you open the article that’s linked, the first paragraph has a link to clackers.
Given that we’re talking about clackers, I figured the entry about “clackers” would describe what they are.
Outside of the entry linked, if you Google “why were clackers banned” you get any number sources.