In a closed environment (not public) where such laws do not apply at all I can see the validity of this requirement. Indeed, even in a public forum I can imagine subscriptions being automatic as a condition of membership as long as people can opt out. The requirement is not unreasonable to me.
However, from my understanding, WWF creates a record "for each user for each subscription" (be it a topic or a whole forum). Therefore, to solve the problem, either an "all forums" record would have to be programmed in, or many subscription records created for each new user and maintained appropriately for each new post...neither happen today.
So...an alternative might be to use NewsPad to bring attention to new posts (laws apply here too) or simply using MS Word to create an email mailshot using based on the author records in the WWF database.
PS...if we are talking about only a few members you might subscribe them manually to each relevant forum.