Dirk Graswinckel

Theodorus Johannes "Dirk" Graswinckel (1 October 1600 – 12 October 1666) was a Dutch jurist, a significant writer on the freedom of the seas. He was a controversialist, who also rose to a high legal position (Fiscal of Holland) where he advised Descartes. He was a cousin and pupil of Grotius. He was also a poet and translator of Thomas à Kempis.
Life.
He was born in Delft, and studied at the University of Leiden. He joined Grotius in Paris in 1624, and later defended him against Johannes a Felden (John De Felde).
"Libertas Veneta" (1634) replied to the anonymous anti-Venetian pamphlet "Squitinio della liberti veneta" (1612). It is in effect also an answer to a work on maritime law by William Welwod.
"Maris liberi vindiciae" attacked Burgus () writing for Genoese pretensions in the Ligurian Sea, but also took on John Selden on the British claim to territorial waters. Selden's Mare Clausum had been published in an English translation in 1652, and he replied the following year with "Ioannis Seldeni vindiciae secundum integritatem existimationis suae". In fact Graswinckel had sent Selden a detailed critique in manuscript in 1635.
In 1651 he published a work "Placcaten, ordonnantien ende reglementen" on the economics of regulation of the grain trade. This came down largely on the side of free trade and the price mechanism. Joseph Schumpeter argued that this was the first clear-cut statement that speculators had a role in the stability of commodity markets.
He died in Mechelen.