Documents to be verified while buying a flat

Hi, i am planning to purchase a 2 bhk flat in Mira road,the owner is settled in USA,they assigned one person in INDIA. with power of attorney , which is signed in front of consulate of Atlanta,which is not registered in India, they are saying that they will sign all the documents in USA and send it though courier before registration and the person who is in India will be available for registration at the Time of registration,I am confused whether in this case the register is allow him to transfer the registration on behalf of owner,is it a a valid procedure for registration?