Oh please. The purpose of copyright law may once have been to protect the public domain, but it hasn't been that for decades, especially since it has constantly been expanded and focused only on protecting profits.
The purpose of copyright law is to protect the profits of greedy companies. This court should know better. Do they not consider recent changes to the law? And how can law have a purpose other than what it actually achieves? No one could possibly read the minds of legislators or the founding fathers on this issue. The purpose of the law cannot be something it never achieves anymore. Of course, going by legal definitions of "reasonable" it's not surprising they reach such an unreasonable, illogical decision. And people wonder why lawyers and judges are so despised with this type of illogical thinking.