No, there isn't. Murder has a specific meaning, and being unlawful is part of it.

Murder has a meaning that predates legal definitions. Also, many groups in history are currently accused of murder despite it being legal at the time. From slave owners to Nazis, from communists to African warlords.

So are these not murders because they are legal?

I’m not claiming that “murder by state” is somehow correct or less evil. My claim is, it’s not a murder; words have their defined meanings.

So Nazis did not commit murder because it was legal. Got it.

They committed genocide. Even worse, obviously, but it fits the definition of word “genocide” better than “murder”, thus I believe we should be using that word instead.

Okay, let’s use another example. Is software piracy stealing? Some people claim it is. I don’t, because words have meanings.