Section 117E(1)(b) in The Patents (Amendment) Act, 2002
(b)in any appeal to the Appellate Board from an order of the Controller on an application for grant of a patent-(i)which is not opposed, and the application is either refused by the Controller or is accepted by him subject to any amendments, modifications, conditions or limitations, or(ii)which has been opposed and the Controller considers that his appearance is necessary in the public interest, and the Controller shall appear in any case if so directed by the Appellate Board.