In this classic of international maritime law he calls for open rights of all countries and dominions to sail the seas without appropriation by any country, which was undoubtedly an attempt to offset the attempts of Spain, Portugal and England to claim sovereignty of the seas. This controversial viewpoint was opposed by John Selden in defense of the British Empire, in Mare Clausum. Grotius [1583-1645] is known principally for this work and his classic treatise on the law of nations, De Jure Belli.