Adam Cohen wrote a piece in the 1 June NYT (on the editorial page) that is both delightful and thought-provoking: "The Lord Justice Hath Ruled: Pringles Are Potato Chips", about a series of British legal decisions.
The question: is a Pringle a potato chip (crisp, in British usage) or (as Procter & Gamble, which makes Pringles, maintained) a "savoury snack". [Cohen reported that P&G claimed that Pringles was a "savory snack", but of course the case was heard in British courts, and the dispute in those courts was about crisps vs. "savoury snacks" -- as in SNACMA (the Snack Nut & Crisp Manufacturers Association), which "represents the interest of the savoury snack industry in the UK". Note that in this usage "savoury snack" is the higher-order category; crisps are savoury snacks, but so are other things.]
There was real money on the line, about $160 million, as Cohen notes:
In Britain, most foods are exempt from the value-added tax, but potato … crisps … and "similar products made from the potato, or from potato flour," are taxable.
(No doubt there's some interesting history as to why the potato, a tuber, should have been distinguished in the law about VAT from cereal plants and nuts, but the history is irrelevant to the Pringles story; the law is as it is, the question being how to apply it in this case.)
P&G argued that Pringles ("which are about 40 percent potato flour, but also contain corn, rice and wheat") should not be considered potato crisps. The VAT and Duties Tribunal disagreed, ruling that (as Cohen quotes):
There are other ingredients, [but a Pringle is] made from potato flour in the sense that one cannot say that it is not made from potato flour, and the proportion of potato flour is significant being over 40 percent.
(I know, you all wanted a comma before being, but apparently the Tribunal didn't use one.)
This decision certainly agrees with ordinary-language usage — anyone who maintained that they hadn't eaten any potato crisps/chips, but only a pile of Pringles (which don't count as crisps/chips because the potato flour in them doesn't constitute the majority of the flour in them) would be rightly jeered — but an appeals court reversed it, saying that Pringles (in Cohen's words) "are exempt from the tax, mainly because they have less potato content than a potato chip."
The Supreme Court of Judicature then reversed this decision, supporting the original Tribunal judgment that, having considered Pringles' appearance, taste, ingredients, process of manufacture, marketing and packaging,
while in many respects [they] are different from potato crisps and so they are near the borderline, they are sufficiently similar to satisfy that test.
(Along the way, Lord Justice Jacob dismissed P&G's claim that to be "made of potato" Pringles would have to be all potato, or nearly so, and was even more scornful about P&G's argument that to be subject to tax, a product must have enough potato in it to have the quality of "potatoness".) Cohen goes on:
In the Pringles litigation, three levels of British courts engaged in a classic debate over line-drawing, a staple of first-year law classes. At some point, a potato-chip-like item is so different from a potato chip that it can no longer be called one — but when? Lord Justice Jacob invoked the wisdom of Justice Holmes: "A tyro thinks to puzzle you by asking where you are going to draw the line and an advocate of more experience will show the arbitrariness of the line proposed by putting cases very near to it on one side or the other.
In other words, sometimes you just have to call them as you see them.
Then Cohen's larger point:
Conservatives like to insist that their judges are strict constructionists, giving the Constitution and statutes their precise meaning and no more [linguists groan here], while judges like [Sonia] Sotermayor are activists. But there is no magic way to interpret terms like "free speech" or "due process" — or potato chip.