Child custody is with legal guardian need to apply child residency

I would like to know that, as a legal guardian as per applied section 7 Guardians and wards act by father by indian court has appointed me as a legal guardian with full custody for my 11 year old son in year 2013. I have full custody of my son according to settlement purses approved by district magistrate in india as mother had given full wright to father including all decision wright to father. My son is with me in New Zealand on student dependent visa since last 1.5 year while myself is in New Zealand since 3 years. As of now i have applied permanent residency application of New Zealand including my son in regards immigration is asking mother’s approval while mother is no more in contact even we don’t know any address or refrence to get her concern. She had also mentioned in settlement purses not to contact her for any reason as all wrights are given to father. In this situation is there any law or option to prove immigration that as per indian constitution if, one parent appointed as legal guardian no need to contact other for movement from india to other country incase minor is with legal guardian.