To put NAN or any other pilot-employing subsidiaries into bankruptcy would be very much a nuclear option. Maybe relevant law would permit it, maybe not - my knowledge of bankruptcy law as applied specifically in Norway is nil.
However - this would likely permanently destroy any kind of mutual respect between pilots working for NAN and the parent airline. If BK wants to pull this trigger, he'd better have very serious contingency options available - like having a large pool of pilots ready to start flying at short notice; wet leasing over a prolonged period will be costly when DY has a fleet of its own sitting unused, and may be unattainable over the spring/summer.
Furthermore, if large numbers of flights are cancelled for a long period of time, it will take far far longer and be very expensive to regain the trust of passengers to book with Norwegian as a reliable airline.
Bluster is cheap, and over a number of years much can be done to further BK's interests, but with what is essentially a large company there's only so much that BK can really do in a short period of time without causing damage to his own long-term interests.