What is the contribution of Hugo Grotius to law?

[Jurisprudence] Hugo Grotius propounded the theory of functional natural law. He built his legal theory on ‘social contract’. He was of the view that political society rests on a ‘social contract’. It is the duty of the sovereign to safeguard the citizens because the former was given power only for that purpose. The sovereign is bound by the natural law. The law of nature is discoverable by man’s reason.