Like Len says, ultimately power rests with the Crown, if that is undermined, then the whole system is in danger of being undermined hence his comment about written constitution. I suppose if his motivations challenge or question the authority of the crown therein lies the issue, but as i am not sure nor am i a constituional expert that is pure speculation and supposition.
It just saddens me that the Judiciary have become embroiled in the whole shebang, but i get why they have no option to do otherwise. It does put the judiciary in a dreadful position.