It's pretty much as the title says. My alliance has over 5 members which is the only requirement I know of for the wolves of warfare event and yet my alliance "Demons Hellhounds" is not at all on the alliance rankings which I can't understand why?
Gallery for proof

as you can see over 5 members and not shown on the rankings?

Hi, can you please link me to your alliance?

That alliance is #40 in the power rankings.