31 March 2012
In Mumbai (Maharashtra) the Registration of "private detective agency" is to be done with the Police Commissioner (law & order dept) and also license has to be obtained under the Arms Act. The local Crime Branch submits the report to the police commissioner, after which registration certificate is granted, subject to compliance of various parameters.
The above should be applicable in Tamil Nadu, and dept. or ministry of "law & order" may be approached for registration formalities.
Every state has a Association of Detective agencies, to which you have to be affiliated.
the central home ministry grants the registration, in consultation with other law enforcement agencies, subject to minimum years of experience.