法華義疏 8.33

8.33

「是諸法之王」者，上十譬十恩但明一方之化即未能自在，今明諸法之王即知化之無方。但於法自在凡有二種：一者、體法自在；二者、化用自在。具二自在，故名法王也。

Regarding 'is the King of all dharmas': the ten parables and ten benevolences above only explained the transformation of a single sphere, and thus had not yet attained sovereignty; now, explaining that he is the King of all dharmas shows that his transformation is boundless. Sovereignty over dharmas generally has two kinds: first, sovereignty over the substance of dharmas; second, sovereignty over transformative functions. Possessing both sovereign powers, he is called the Dharma King.