Full Idea
For Grotius, there was a fundamental 'natural right' of self-preservation upon which all known moralities and codes of social behaviour must have been constructed, but it is balanced by a fundament duty or 'natural law' to abstain from harming others.
Gist of Idea
A natural right of self-preservation is balanced by a natural law to avoid unnecessary harm
Source
report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.2
Book Reference
Tuck,Richard: 'Hobbes: a very short introduction' [OUP 2002], p.61
A Reaction
This theory has the virtue of economy, but I don't see how you can clearly justify those particular natural rights and laws, without allowing others to creep in, such as a right to a decent share of food, or a law requiring some fairness.