1) your father cannot purchase land belonging to Scheduled tribe
2) SC has ruled that non Dalits cannot buy land belonging to SC and ST
3) A.P. Assigned Lands (Prohibition of Transfers) Act, 1977 prohibits alienation of assigned lands. While Section 3 renders all categories of transfers of assigned land, as void ab initio,
4) Section 5 prohibits the registration of any document, evidencing such transfers. Any sale or transfer, in contravention of the provisions of the Act, cannot change the character of land, and the objection can be raised at any point of time. Successive transactions, which are otherwise prohibited, do not bring about any change as to the legal implications.