Doing a search on the Internet, I found the Norwegian Sale of Goods Act at the following website: http://www.jus.uio.no/lm/norway.sog.act.1988/doc.html(posted 8351 days ago)Is this what you are referring to, or is it a UK law? Which exact section of the act did you find "fitness for purpose".
In the US all commercial products carry an implied warranty of fitness for a particular purpose. A product that broke down after 15 months would not likely violate this implied warranty. In the US, the fitness for a particular purpose implied warranty does not usually relate the reliability of a product, unless the majority of samples of the product broke very soon after initial use. Do you know whether your problem is symptomatic of similar problems others have had with camera (do you have any quantitative evidence about its reliability)?