Emmerich de Vatel
Emer de Vattel (1714-1767) was one of the foremost theorists of natural law in
the 18th century. His writings were widely read in the American colonies and
had a profound impact on the thinking of the Founding  Fathers.
Emmerich de Vattel's text, "The Law of Nations" was crucial in shaping
American thinking about the nature of constitutions.

American writers quoted {The Law of Nations} on constitutional law, almost
immediately after the book's publication. Samuel Adams wrote in 1772, “
Vattel tells us plainly and without hesitation, that the supreme legislative
cannot change the constitution, that their authority does not extend so far, and
that they ought to consider the fundamental laws as sacred, if the nation has
not, in very express terms, given them power to change them.”

The Constitutional Congress in 1787, adopted a constitution based on Vattel’s
principles rather than British legal doctrine.  British legal experts such as
Blackstone argued that the Parliament and King could change the constitution.
This legal argument was seen by the Americans as proposing arbitrary power.
The early revolutionary leaders' emphasis on Vattel as the authority on
constitutional law, with his conception that a nation must choose the best
constitution to ensure its perfection and happiness, had very fortunate
consequences for the United States and the world, when the U.S. Constitution
was later written.  
The Law of Nations