I can hear you asking the question - So what sort of rules, can be used for wargaming?
The answer is. Any rules really, but I would think that any any rules which were written for 28mm - 54mm figures could easily be used for Lego wargaming. Things like Warhammer (fantasy and 40K0, Warmachine, Songs of Blades and Heroes, Nuts, the list goes on and on.
There are also some rules which have been written specifically for wargaming with Lego, and I have compiled a list of the more popular ones:
BattleBrik
Wargaming with Lego
battlebrik.wordpress.com
BOW (Bricks Only Wargame)
Another Wargame system for LEGO® bricks
bow.lswproject.com/
BrikWars
The plastic-brick wargaming system of chaos and destruction
www.brikwars.com/
Lego OGRE
Building OGRE miniatures with LEGO bricks
http://www.efran.org/embassy/lego-ogre.html
Lego War Game
Turn-based Lego war game
http://www.mocpages.com/moc.php/65268
