In 1494, two years after Columbus's first voyage, Spain and Portugal signed a treaty drawing a line down a map of the world — formalising a division the Borgia pope Alexander VI had decreed the year before — that gave everything west of it to Spain and everything east to Portugal. Neither country had yet seen most of what they were being awarded, and no one consulted the people who lived there. The Treaty of Tordesillas is the founding document of modern colonialism as a juridical project. It is why Brazil speaks Portuguese while the rest of South America speaks Spanish — Portugal's slice happened to clip the South American bulge — and why nobody's colonization scheme treated native sovereignty as a serious legal matter for the next four centuries.
Tordesillas illustrates a recurring pattern: European powers settling their disputes among themselves over territories they did not own. The line was drawn 370 leagues west of the Cape Verde islands — a figure haggled up from the pope's original 100, with no reference to any feature on the ground and no reliable way to fix longitude at sea, which is why the treaty's antipodal half later sparked a second quarrel over the Moluccas, settled only in 1529 at Zaragoza. Tordesillas itself rested on papal donation — the bull Inter caetera — rather than on emptiness: the pope claimed authority to dispose of all non-Christian lands, and the two crowns simply divided the grant. The generalising move came later, with the doctrine of terra nullius, which held that lands inhabited by non-Christian peoples were legally empty and available for Christian appropriation. That doctrine was debated by the Salamanca theologian Vitoria, who insisted Indians were rational owners yet still found grounds for conquest, secularised by Grotius into European international law, and formed the legal scaffolding of empire until decolonization. Other powers that had been frozen out — France's Francis I famously demanded to see 'the clause in Adam's will' excluding him — simply ignored the line, and by the seventeenth century the Dutch and English were carving their own empires regardless. It was repudiated in Australian common law by the High Court's 1992 Mabo decision — which finally recognised that Aboriginal people had held the continent all along — and is still litigated in indigenous-title cases worldwide.
In 2023 the Vatican formally repudiated the Doctrine of Discovery, the chain of fifteenth-century bulls that licensed Tordesillas, after decades of pressure from indigenous Catholics — a sign of how live this history still is. The deeper framework, territorial sovereignty as a thing European states grant each other, persists in subtler forms in international law, which is why the Westphalian system has always sat uneasily with the claims of indigenous peoples, refugees, and stateless populations who were never parties to the bargain.