Full Idea
Hobbes's position is that we have a duty to obey the Laws of Nature when others around us are known (or can reasonably be expected) to be obeying them too, and so our compliance will not be exploited.
Gist of Idea
We should obey the laws of nature, provided other people are also obeying them
Source
report of Thomas Hobbes (Leviathan [1651]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 1 'Hobbes'
Book Reference
Wolff,Jonathan: 'An Introduction to Political Philosophy (Rev)' [OUP 2006], p.16
A Reaction
In particular, we should keep contracts. Hobbes doesn't seem fully committed to keeping facts and values separate.