See your brother in law can execute a registered confirmation deed in favour of the buyer. 

Though in case brother in law is not having objection it is not.illegal but same is not done properly so a confirmation/rectification deed for same can be made and registered, confirming the transaction.

Notarised gpa is not valid in eyes of law. Any sale or transfer on the same is illegal. Supreme court has barred the transfer through GPA.

GPA ought to have been registered to enable you to execute sake deed in favour of purchaser 

your brother in law can execute deed of confirmation 

deed of confirmation should be duly stamped  and registered 

Better your brotherjn law execute a confirmation deed. confirmation deed means assent to the estate already created. By the confirmation, the parties further strengthen and give legal validity to the estate. A person may confirm and assent documents of conveyance executed by another person.. 

1. i do not know about your state, but in Maharashtra, if a GPA contains a clause for 'power to sell' then it has to be compulsorily stamped and registered if such GPA is given to non specified persons 

2. since your brother in law is agreeable to the transaction done by you, a deed of confirmation can be executed and registered, in which you will be the vendor and you brother in law will be the confirming party

3. this will clear all doubts in the minds of the buyer and he will also get a clear title to the land if its owner himself agrees and confirms the transaction between you and the buyer before the confirmation deed 

1. As per the information mentioned in the present query, makes it clear that whatever you did, you did in the garb of the GPA, executed by the owner/ brother in law.
2. Let me tell you that as per the recent judgment of our Hon’ble Supreme Court That for any property transaction, GPA or POA or SPA would not hold legality/ sanctity.
3. But, it has some exception that if the same has been executed in the favour of a close relative then it may have legal sanctity.
4. But, it has to be ascertain as to whether you fall under that category/ exception or not.
5. On the other side, you should not be worried as the transaction was executed long time back from 2017 (year of Supreme Court judgment) and the law doesn’t implement retrospectively on you.
6. You need not to worry about the transaction which you executed, and no one can put any question on it and if someone does that then you will be in a state of “winning”.

Dear Sir,

According to Supreme Court land mark judgment GPA sales are banned from 2011.  As such it is better to ask your brother in law to execute regular Sale deed by referring earlier sale deed and GPA and thus you can legalise the transaction.

Dear Cleint,

The sale is invalid. It was to be executed by you as POA and not actual seller. Get it rectify by applying sub registrar office that sale is executed through POA holder.

You might have sold the property by playing fraud on the registrar either by forging his signature or impersonating him which is illegal and invalid.

It cannot be rectified but can be ratified.