Grant v Allan 1987 JC 71. In short, an employee was prosecuted for making copies of confidential information to sell to his employer's business rivals. He said "this isn't a crime", and the sheriff (first-instance judge) rejected his argument, but on appeal the High Court said he was right.

By the way, in Scots criminal law the prosecution doesn't have to name the crime it thinks you've committed. It just has to say what it claims you did, and if the charge discloses any crime, it will be relevant. In this case that is precisely how the prosecution went about it: they didn't mention the word "theft" at all. So what this case means is that copying confidential information isn't a crime at all, not just that it isn't theft.

However, it is totally uncontroversial that what he allegedly did constituted the delict of "breach of confidence".

(You'll note that I didn't say he actually did it. This is because he successfully defended himself by saying "what I'm accused of isn't a crime", so the prosecution never got a chance to prove he did it.)