Nomination in joint accounts being not allowed?

If the joint acount is on the basis of E or S then anyone cannot unilaterally appoint a nominee hich would be agaisnt the interest of the other account holder, besides since it is an either or survivor arrangement the survivor can very well take the entire money without giving anything to the nomninee or the legal heirs. 

There is no legal infirmty in  BOI rejecting the proposal to appoint nominee made by the senior citizen joint account holder.

If the accoount mandates that all the account holders have to sign the papers every time for each and every transaction of any kind then there is no question of anyone doing any fraudulent act ot cheat the other two.

YThe concept of nominating someone to your account is to benefit the nominee after his lifetime, so there are various modes to transfer the monies of the account to the beneficiary if he still insists on nomination, then he can approach the bank to register the person as his nominee as per the bank rules, if the bank refuses then he can think about taking it legally 

If an account is in the name of more than one person, whatever may be the mode of operation any nomination will come into effect only if and when all the account holders are dead. Normally all the account holders have to sign the nomination form.