More or less all tariffs and sales tax systems are like this; the rules are _always_ kind of all over the place.

My personal favourite example is when the Irish Supreme Court determined that Subway bread was not bread: https://www.theguardian.com/world/2020/oct/01/irish-court-ru... (Bread had advantageous treatment for VAT purposes, but Subway's 'bread' has too much sugar to qualify.)

There's also the famous Jaffa Cake case, of course: https://en.wikipedia.org/wiki/Jaffa_Cakes#Legal_status , but I think the Subway one has an extra element of absurdity because it went all the way to the _Supreme Court_.