Can you murder even in the absence of a law?

Oxford defines these words as follows:

This is how I interpret this: without a law no action can be lawfull (obviously) so all actions automatically become unlawfull because of the law of the excluded middle. This also makes sense to me since no action can comform with, be permited by or recognized by a law if no such thing exists. But an action cannot be illegal without a law.  

What do you guys think? Does this make sense? Or should the definition of murder be changed from unlawfull to illegal?

Sometimes definitions arent well defined to suit all situations.

Since law defined what is unlawfull, and group who makes the law decided that only it can make the law,

there is simply no way for your actions to be permitted by a group if the group doesnt exist.

And as long as definition of unlawfull requires that, it makes everything unlawful by that definition in that scenario.

Its more of a definition issue,

Where before law is created, everything is unlawfull (non-approved by law).

There should be a legal definition and a moral definition.

The legal definition would be illegal killing

The moral definition would be immoral killing

The law is always an imperfect implementation of a potentially imperfect moral theory. Those who understand this have no trouble distinguishing when to use which definition.

Having only a legal definition would necessarily constrain the concept to the context of place and time (for every government). Anyone who believes that would be unable to say the nazis murdered jews if the nazis made killing jews lawful killing (which they didn't in a super official way but they would have if they needed to)

Double check with a consensus.

I like your thought process!

edit:reread your question. There is always a law the eternal law which I will debate and lose on the matter of at a future time. Peace :)

The similar issue was brought up at Nuremberg trials. 

Its only illegal if you get caught.