Sherry Singer and Indie Sing were the two international trade lawyers working for Marvel Comics in the ’90s (and they were ladies, we feel obligated to mention by the mandate of the site), who took a look at the Harmonized Tariff Schedule, a book full of customs regulations, and realized that “dolls” were taxed 12% on import, while “toys” were taxed only 6.8%. The difference between the two was that a doll “represented only a human being,” while “toys” were ”monsters, robots, angels, basically anything that isn’t “only representing a human.” Probably, at some point in the past, some American doll manufacturer had felt threatened by overseas competition, and had lobbied the government to put a tax on imported dolls.
There’s also a link at The Mary Sue to a podcast that explains how the case turned out, so click on over there to find out the resolution.