In the year 67 BCE, the Roman Senate passed the Lex Gabinia and gave Gnaeus Pompeius Magnus — Pompey the Great — an extraordinary and unprecedented command. They gave him imperium — supreme military authority — over the entire Mediterranean Sea and every territory within fifty miles of its shores. For three years, he would have the authority of a proconsul across the entire Mediterranean world. He would command every Roman fleet and every Roman army in the region. He would have the authority to make war, negotiate peace, and administer justice anywhere within his vast jurisdiction.

The immediate purpose was to destroy the Cilician pirates who had been disrupting Roman trade for decades. Pompey accomplished this in three months — a military and logistical achievement of extraordinary efficiency. But the larger significance of the Lex Gabinia was not tactical. It was constitutional. For the first time in history, a sovereign state had claimed legal jurisdiction over an entire ocean — not merely the shores and ports within its territory, but the open water itself. The Mediterranean was not a shared international commons. It was, by Roman legal declaration, Roman. It was Mare Nostrum: Our Sea.

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Dominium, Imperium and the Legal Vocabulary of Colonial Control

Roman law gave the Atlantic colonial project its legal vocabulary. The two concepts most central to that vocabulary are dominium and imperium, and understanding the distinction between them is essential to understanding how colonial law operated.

Dominium is property ownership — the legal right to exclude others from land or goods and to use them as the owner sees fit. In Roman law, dominium was absolute: the owner could use, abuse, transfer or destroy property at will. Crucially, the law of dominium applied to slaves as well as to land and goods. A slave was the dominium of their owner. There was no legal distinction between the slave owner’s right to their land and their right to their slave. Both were property rights. Both were absolute. This is why the Zong massacre was not a criminal matter under English law in 1781 — it was a property insurance claim. The enslaved people who were thrown overboard were dominium.

Imperium is the authority to govern — the legitimate power to make laws, administer justice and use force in the territory under one’s jurisdiction. In Roman constitutional theory, imperium derived from the Roman people and was delegated to magistrates and military commanders for specific purposes and periods. But in practice, as Rome’s empire expanded, imperium became the authority of the Roman state to claim jurisdiction over any territory it could militarily dominate — and to declare that the governance structures of peoples within that territory were legally subordinate to Roman authority.

Read the Papal Bull Romanus Pontifex of 1455, which authorized Portugal to claim, conquer and enslave any non-Christian peoples it encountered. Its legal logic is Roman: the Portuguese crown has dominium over the lands it discovers, and imperium over the peoples within them. The vocabulary is Latin. The concepts are Roman. The application is colonial. Five hundred years separate the Lex Gabinia from Romanus Pontifex. The legal architecture is continuous.

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The Jus Gentium — The Law of Nations and Its Deceptions

Roman law developed a concept called the Jus Gentium — the Law of Nations — to address legal questions arising in the relationships between Romans and non-Romans. In principle, the Jus Gentium was a body of legal principles considered universal — applying to all peoples everywhere, derived from reason and natural law rather than from the specific traditions of any particular community.

In practice, the Jus Gentium served two functions that were in direct tension with each other. On one hand, it provided a framework for commercial and diplomatic relations between Rome and foreign states that recognized those states as having some degree of legal standing — allowing them to enter treaties, conduct trade, and seek redress for injuries under principles that both parties acknowledged. On the other hand, it developed the concept of hostes — public enemies — who stood outside the protection of any law. Pirates and other irregular fighters were hostes. They had no legal standing. They could be killed, enslaved or subjected to any treatment the captors chose, with no legal accountability.

When colonial legal theory needed to explain why the sovereign peoples of the Americas, Africa and Asia could be conquered, enslaved and dispossessed, it reached for the Jus Gentium’s concept of hostes. The non-Christian peoples of the world were, by definition, outside the community of nations that the Jus Gentium recognized. They were not parties to the system of international law. They were, legally, no better than pirates — people who existed in a legal state of nature, subject to whatever a Christian sovereign chose to do with them.

The Maroon communities inverted this argument with devastating precision. By forcing colonial governments to sign bilateral treaties, they inserted themselves into the very system of international law that had declared them non-persons. A treaty between the British Crown and the Windward Maroons of Jamaica is, in the vocabulary of the Jus Gentium itself, a recognition of Maroon sovereignty. The British Crown could not simultaneously claim that the Maroons were hostes — outside the law — and sign a binding treaty with them as if they were a sovereign people. The treaty was a legal admission that the Maroons were right.

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Roman Admiralty Law and the Template for the Slave Trade

Roman admiralty law — the law governing ships, maritime commerce and incidents at sea — was the most developed and internationally influential body of law in the ancient world. The Rhodian Sea Law, which Rome adopted in the first century BCE, established principles of cargo liability, general average (shared loss in maritime emergencies), salvage rights and the legal status of cargo on board ships that were still in force in the sixteenth century when Atlantic commercial shipping began in earnest.

The legal status of cargo under Roman admiralty law was straightforward: cargo was property. It belonged to its documented owner. The ship’s captain had a duty of care for the cargo. If cargo was lost through negligence, the captain was liable to the owner. If cargo had to be jettisoned in an emergency to save the ship, the loss was distributed proportionally among all the cargo owners under the doctrine of general average. The captain’s decisions about cargo — including the decision to jettison it — were commercial decisions governed by property law.

The Atlantic slave trade applied this legal framework, unchanged, to human beings. Enslaved people were cargo. They were listed on cargo manifests alongside bales of cloth and barrels of gunpowder. Their loss at sea was a cargo loss. The Zong case of 1781 was litigated not as a murder trial but as an insurance claim, because under the Roman admiralty law principles still in force in English maritime law in 1781, the question before the court was whether the “cargo” had been jettisoned under circumstances that allowed the insurers to be held liable for the loss. The court ruled that the insurers were not liable — not because throwing 133 people into the sea was legal, but because the captain had not established sufficient necessity. The frame was Roman. The cargo was human. The logic was continuous.

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The Pax Romana as Colonial Template

The Roman Empire justified its expansion through the concept of the Pax Romana — the Roman Peace. The argument was that Roman conquest, however violent in its initial phase, produced a stable, prosperous, law-governed order that was ultimately better for everyone than the disorder and conflict that preceded it. The conquered peoples of Britain, Gaul, Spain and North Africa were not victims of imperial aggression. They were beneficiaries of civilization.

This argument — that conquest is ultimately a gift to the conquered — is the foundational ideological claim of every colonial project in history. The Spanish brought Christianity and civilization to the Americas. The British brought law and order to India and Africa. The French brought the mission civilisatrice to West Africa and Southeast Asia. The specific content of the claimed gift changes. The structure of the argument is Roman. And the Aristotelian framework of natural slavery — that some peoples are inherently suited to be governed by others — is always available as the philosophical backstop when the civilizational gift argument is insufficient.

The Maroon communities rejected both arguments in the most direct possible way: by building sovereign, self-governing communities that were, by every observable measure, more stable, more just and more functional than the plantation systems that colonial law imposed on the surrounding territories. The Pax Romana said: you need our law. The mountains of Jamaica said: we have our own.