In order to qualify for protection, a work must be an expression with a degree of originality, and it must be in a fixed medium, such as written down on paper or recorded digitally. The idea itself is not protected. That is, a copy of someone else's original idea is not infringing unless it copies that person's unique, tangible expression of the idea. Some of these limitations, especially regarding <answer>what qualifies as original</answer>, are embodied only in case law (judicial precedent), rather than in statutes.
What limitation is only embodied in case law, rather than statues?
what qualifies as original