Battleground: Fantasy Warfare design

This is just a clarification that a design like this can't be copyrighted. I got the idea to use (or steal) the idea from Battleground (http://www.yourmovegames.com/battleground_index.html) of printing a combat unit on card to then move around. Essentially creating a miniatures game without the miniatures. However, is this breaching any type of law?
I guess not as then all counter wargames would be breaching copyright laws. Wings of War uses the same design as Battleground, just uses planes instead.
But I just want to cover my back by making sure that I can do that (just make sure the rules themselves are different)