(2) Where a licensee is granted under subsection (1) of this section (a) the licence shall be registered, and shall be of no effect against third parties until registration is effected and the prescribed fee paid; and (b) the registration shall be cancelled at the request of the licensor if the Registrar is satisfied that the licence, has been terminated. (3) Any clause in a contract for a license under subsection (1) of this section is null and void in so far as it imposes on the licensee in the industrial or commercial field restrictions which do not derive from the rights conferred by the relevant patent or design or are necessary for the safeguarding of those rights Provided that(a) limitations concerning the scope, extent, territory or duration of the exploitation of the patent or design or the quality or quantity of the products in connection with which the patent or design may be exploited; (b) obligations imposed on the licensee to abstain from all acts capable of prejudicing the validity of the patent or the validity of the registration of the design; and (c) in the case of a patent, limitations justified by the interest of the licensor in the technically efficient exploitation of the subject of the patent, are not restrictions of the kind mentioned in this subsection. (4) In the absence of any provision to the contrary in a contract for a licence under subsection (1) of this section(a) the grant of the licence shall not prevent the licensor from(i) granting further licences to other persons, or (ii) himself exploiting the relevant patent or design; (b) the licensee shall not be assignable by the licensee; and (c) the licensee shall not be entitled to grant further licenses. (5) Where a contract under subsection (1) of this section provides for a licensee to grant further licences, this section shall apply in relation to any such further license as it applies in relation to license granted under the said subsection (1). (6) The Minister, if he is satisfied that it is in the interest of Nigeria and its economic development to do so, may by order in the Federal Gazette provide that contracts under subsection (1) of this section (or any specified class thereof) shall, in so far as they involve the payment of royalties outside Nigeria, be invalid without the approval of such authority as may be specified in the order. 24. (1) Subject to this section, a person's rights in a patent application, in an application for the registration of a design, in a patent or in a registered design may be assigned, transferred by succession or held in joint ownership. (2) An assignment under subsection (1) of this section shall be in writing and signed by the parties. (3) An assignment or transfer by succession under subsection (1) of this section shall have no effect against third parties unless it has been registered and the prescribed fee paid. (4) In the absence of any provision to the contrary among themselves, joint owners of a patent or registered design may separately transfer their shares, exploit the patented invention, utilise the registered design or exercise the rights conferred by section 6 or 9 of this Act, as the case may be; but a licensee under this Act may not be granted by joint owners otherwise than jointly.