2019 marks the silver anniversary of the WTO TRIPS Agreement. Policymakers and commentators remain deeply divided about the strengths and limitations of this agreement. On the one hand, they marvel at its success in establishing international minimum standards for the protection and enforcement of intellectual property rights. On the other hand, they widely criticize the agreement for imposing high "one size fits all" standards upon developing countries.

Regardless of one's perspective, the harmonization project advanced by the TRIPS Agreement, and continued through TRIPS-plus bilateral, regional and plurilateral agreements, has been at the forefront of the international intellectual property debate. While this article is interested in exploring this continuously controversial project, the discussion will focus on a topic that international intellectual property scholars have underexplored: the limits to TRIPS harmonization.

To help examine these limits, this article focuses on the protection of undisclosed test or other data for pharmaceutical and agrochemical products. It begins by discussing issues on which the TRIPS negotiating parties had achieved consensus or had failed to do so. The article then examines the negotiation of new international minimum standards under the TPP Agreement, the proposed RCEP Agreement and the recently completed United States–Mexico–Canada Agreement (USMCA).

The article continues to identify three sets of additional complications that have affected the efforts to develop international minimum standards at both the multilateral and nonmultilateral levels. Specifically, the article examines the arrival of new technologies, new politics and new regimes. It concludes by drawing six distinct lessons regarding the TRIPS harmonization project.