Section 23, The Patents and Industrial Design Act, 2012

(1) The rights under the patent shall not extend- (a) to acts in respect of articles which have been put on the market in any country by the owner of the patent or with his consent; or (b) to the use of articles on aircraft, land vehicles or vessels of other countries which temporarily or accidentally enter the airspace, territory or waters of Sierra Leone; (c) to acts done only for experimental purposes relating to a patented invention; or (d) to acts performed by any person who in good faith, before the filing or, where priority is claimed, the priority date of the application on which the patent is granted in Sierra Leone, and was using the invention or was making effective and serious preparations for such use. (2) The right of prior user referred to in paragraph (d) of subsection (1) may be transferred or devolved only together with the enterprise or business, or with that part of the enterprise or business, in which the use or preparations for use have been made.