Literature on constitution-making has traditionally focused either on the homogenous, transnational nature of constitutions, or conversely, on how domestic drafters or indigenous cultures work to shape a unique national product. This Article shows that these international and domestic perspectives can be reconciled under one framework. Using quantitative analysis and a case study of the constitutional process for the world’s newest nation, South Sudan, this Article demonstrates how these dual constitutional influences impact the two main components of constitutions — human rights provisions and structural/institutional framework — differently and predictably. In what I term an “intermestic constitution,” transnational forces disproportionately influence constitutional rights provisions, and domestic forces disproportionately affect constitutional structural provisions. Drawing on strategic-realist theories of constitution-making, this Article postulates that four elements — three based in the socioeconomics and the domestic politics of the drafting country and one based in geopolitical politics — are key predictors of when an intermestic constitution will emerge.These findings have both theoretical and practical implications. On a theoretical level, they offer new insights into the literature on comparative constitutional design, demonstrating how constitutional influence can be methodically dualistic and reconceptualizing the transnational versus national influence dichotomy. On a practical level, they spell out a recipe for intermestic constitutions in other nations, and predict how those documents will perform. This Article cautions that where intermestic constitutions materialize, indigenous structures designed to bolster power of drafters and would-be leaders may concentrate power in the executive, subvert an independent judiciary, or otherwise diminish checks and balances, thereby undercutting the constitution’s robust, internationally-approved progressive bill of rights.