Oversight of the lawmakers
The point the judge makes is that both in the law (Wetboek van Strafrecht 80sexies) and in the 'Memorandum of Understanding' during the creation of the law, they only considered devices ('automated works') that store (in a non-transient form), (substantially) process *and* transmit data. According to the judge a router fails that test because it does not 1) store (non-transient) the data sent, and 2 does not process the data beyond what is necessary for transmission.
Secondary, the judge finds that the computer crime law (Wetboek van Strafrecht 138a) according to the legal history was intended for protection of those who 'through actual security measures have made clear that they want to shield their data/information from prying eyes'.
As the defendant did not break into a computer (80sexies), and the misuse / misappropriation of a connection is not covered in law (138a), the defendant was cleared of that charge.