> Norway has civil law rather than common law - doesn't this mean that this decision doesn't work as precedent, as that's only really seen in common law?

Precedent exists in civil law systems also. The difference is that in civil law systems precedent is generally seen as persuasive rather than binding, and lower-level judges have greater freedom to disregard precedent than in common law systems. That said, I think the difference between common law and civil law systems is a matter of degree rather than a stark boundary. Even when they aren't formally speaking bound by precedent, lower civil law courts will tend to respect the past rulings of the higher courts and apply them–no judge likes being overturned on appeal. And, in common law systems, not all precedents are binding, some are merely persuasive; and there is the procedure of "distinguishing" – https://en.wikipedia.org/wiki/Distinguishing – which enables judges to justify not following a precedent even while still formally affirming it as binding.