In reference to your comment on Narnian's answer, my guess is that since Satan is referred to as the "prince of this world" (John 12:31, 14:30), it's been misconstrued over the years to mean "ruler" &/or "king". Along the same lines, since we understand he'll be in Hell for eternity, people have associated the "prince of this world" and "will be in hell" together and, voila, you have a "King."
Wikipedia states (emphasis added):
God therefore grants [Satan] the chance to test Job. Due to this,
it has been interpreted that [Satan] is under God's control and
cannot act without God's permission. This is further shown in the
epilogue of Job in which God is speaking to Job, [Satan] is absent
from these dialogues. "For Job, for [Job's] friends, and for the
narrator, it is ultimately [God] himself who is responsible for Job's
suffering; as [God] says to the 'satan', 'You have incited me against
him, to destroy him for no reason.'".
I'd say from observation that a King usually does not need permission to do such things.
This is mostly an educated guess, though :)