50, CAP. 400] Avoidance of certain restrictive conditions in contracts Patents 49. (1) It shall not be lawful in any contract made after the com­ mencement of this Act in relation to the sale or lease of or a licence to use or work any article or process protected by a patent to insert a condition the effect of which will be­ (a) to prohibit or restrict the purchaser, lessee or licensee from using any article or class of articles, whether patented or not, or any patented process, supplied or owned by any per­ son other than the seller, lessor or licensor or his nominee; or (b) to require the purchaser, lessee or licensee to acquire from the seller, lessor or licensor or his nominee any article or class of articles not protected by the patent; and any such condition shall be null and void, as being in restraint of trade and contrary to public policy: Provided that this subsection shall not apply if­ (i) the seller, lessor or licensor proves that at the time the contract was entered into, the purchaser, lessee or licensee had the option of purchasing the article or obtaining a lease or licence on reasonable terms without such conditions as aforesaid; and (ii) the contract entitles the purchaser, lessee or licensee to relieve himself of his liability to observe any such conditionon giving the other party three months' notice in writing and on payment, if the Registrar so directs, of compensation for such relief, in the case of a purchase of such sum, or in case of a lease or licence of such rent or royalty for the residue of the term of the contract, as may be fixed by the Registrar. An appeal shall lie from any decision of the Registrar under pro­ viso (ii). (2) Any contract relating to the lease of or licence to use or work any patented article or patented process may, at any time after the patent or all the patents by which the article or process was protected in Zambia at the time of the making of the contract has or have ceased to be in force, and notwithstanding anything to the contrary in the same or in any other contract, be determined by either party on giving three months' notice in writing to the other party. (3) Nothing in this section shall­ (a) affect any condition in a contract whereby any person is prohibited from selling any goods other than those of a par­ ticular person; (b) be construed as validating any contract which would, apart from this section, be invalid;