The history of patent law harmonization goes back to the adoption of the Paris Convention for the Protection of Industrial Property in 1883.
A century later, in 1983, discussions began on the legal effects of an international grace period on patent law. The scope of that work was gradually expanded and evolved, through the efforts of the Committee of Experts, into a draft Treaty Supplementing the Paris Convention as far as Patents are Concerned. The text of the draft Treaty (the “Basic Proposal”) was discussed at the Diplomatic Conference on the Conclusion of a Treaty Supplementing the Paris Convention as far as Patents are Concerned in 1991, which could not adopt a new treaty.
In the aftermath of the failed 1991 Diplomatic Conference, many provisions of the Basic Proposal, including, inter alia, those relating to the term of patent protection, rights conferred by a patent and non-discrimination as to field of technology, were incorporated into the Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS Agreement). However, other issues, such as novelty and inventive step, were left unresolved.
From 1995, discussions in WIPO focused on formality requirements under patent laws. These talks resulted in the adoption of the Patent Law Treaty (PLT) by the Diplomatic Conference on June 1, 2000, which harmonizes and streamlines formal procedures in respect of national and regional patent applications and patents.
In November 2000, the need for patent law harmonization going beyond formalities, led WIPO's Standing Committee on the Law of Patents (SCP), at its fourth session, to decide to initiate work on harmonization of substantive patent law with a view to concluding a Substantive Patent Law Treaty (SPLT). Different views on patent law harmonization among the WIPO Member States, however, emerged as the SPLT negotiation moved forward, and the sensitivity of this issue was highlighted. Consequently, the negotiation was put on hold in 2006. More on the draft SPLT can be found here.