I could find this article, it is old 23/Sep/14 but it says that Central Govt. bill tabled in Lok Sabha in May-12 was rejected by the standing committee on finance. Therefore is right to conclude there is no law governing MFI till a bill is passed by Parliament.
RBI is a regulator which regulates NBFC-MFI and not the MFI registered as society in the States.
Therefore it may be right to speculated that NBFC-MFI may be less susceptible to State Govt. interference.