The claim has to be made by the leader(s) or a high ranking official (top 3 people).
You cannot from now have a war claim accepted by someone in your faction. Otherwise it is unfair. For instance: Someone in my faction could put one up now and then I accept it and the other team does not entirely know until I have waged war on them on the server.
Also the claim has to have 1 weeks notice as for everybody to know and get their defences ready. -Only fair. This will also depict medieval times which the sever is aiming for in PvP.
This is just for fairness and enjoyment of the other players game.