You cant http://www.copyright.gov/fls/fl108.htmlAdmiral-Badruck wrote:I heard that you cannot copyright game rules. But I guess that's not the problem. I think the space hulk of WFB is mordheim or blood bowl either one would be fine with me.
However, according to that article you CAN copyright the rulebook as literature meaning someone CAN copy your rules but they have to word them in a completely different fashion, which would be an absolute pain of a task to do.
Simpler just to create your own unique game along the same lines a-la Advanced Herequest, Warhammer Quest, Talisman etc.