IA's legality in general has apparently never been tested in court,
A bit too generic a statement; I assume you're talking only of the legality of giving public access to Wayback copyright-eligible all rights reserved content. IA follows a standard which is designed to avoid litigation: http://www2.sims.berkeley.edu/research/conferences/aps/removal-policy.html Until the Oakland Archive Policy is supersed, they're not going to change their policies. Is there an alternative standard that one (e.g. Wikimedia) could adopt? If not, who's going to make one? Probably netpreserve.org and IFLA would need to be involved at least.
Nemo