When your Ranked 3 (or lower) in your guild and you access the Register Tab from Guild Wars menu:
1) If your guild is registered for next week's GW, show a message like "Your guild is already registered for next week's guild war."
2) If it's not, then it's ok to show the message that's being shown for both cases: "Only guild leaders and rank 2 officer can register."
I say this because there was someone in my guild already asking me if the can't participate because they're not rank 2. We're registered already, but they don't have a way of knowing (except from me, ofc) that the guild is indeed registered.