“You can shoot a man with impunity, but you’d better not steal his cow”

Cows have value in Texas. This saying (not found elsewhere with these words) dramatically illustrates the point.
 
 
12 January 1936, Abilene (TX) Morning Reporter-News, pg. 4, col. 1:
It calls to mind the old Texas saying that you could shoot a man with impunity, but you’d better not steal his cow. There is still a large element of truth in that.