People in general tend to agree that they themselves, and perhaps others, should be treated according to certain standards. Unless someone's been raised to believe they're deserving of violence (unfortunately all too common in some places/groups), they would expect to be able to walk down the street without being hit in the face, for example.
Human rights legislation operates on the same principle. People agree that "we should treat people this way, so let's make a law that says it's a right". Then, hopefully, if this right is violated by someone, they will be punished according to the guidelines. No god/supreme being is really required.
I'm actually inclined to believe that the idea of God being the only 'true' moral force, and therefore having the greatest authority to punish you (and only when you die) is kind of an authorization to deny other humans' rights. God will take care of it all in the end. Apparently, if you're really evil, He may even take you out with a lightning bolt, or some such. What, then, is the point of being punished by earthly authority? One can use the obvious fact that you're still here as an implied approval of your actions; by God, no less.
