<p>Regional trade agreements offer a path to regulatory conformity and smoother trade flows. This paper examines how regulatory quality relates to global value chain (GVC) participation within Regional Comprehensive Economic Partnership (RCEP). Using Organization for Economic Co-operation and Development (OECD) Trade in Value Added (TiVA) data for 2009–2020 and the World Governance Indicator (WGI) regulatory quality indicator, we estimate a two-way fixed effects model with a quadratic term to identify curvature. The core results are margin specific. Backward participation follows an inverted U. At low baselines the marginal benefit of clearer rules exceeds the marginal cost of compliance, but as regulatory accumulation rises, recurrent compliance and coordination costs grow, and the net payoff diminishes. Forward participation is U-shaped. Benefits emerge mainly at higher credibility when partners accept domestic standards, testing, and conformity assessment, so marginal benefits begin to dominate marginal costs. Heterogeneity is pronounced. Members below the turning point see positive marginal effects on the backward margin, while frontier countries such as Singapore and Japan often show flat or negative effects that reflect diminishing returns and upstream specialisation rather than regulatory excess. Results are robust across alternative specifications and inference checks. The estimated turning points are descriptive, within-sample markers that inform sequencing, not numerical policy targets.</p>