How will the halo reach armor codes work for offline players

If you have an Xbox Live account, but simply choose not to sign in often then you can still use the armor codes to download the skins, and you can use the armor in custom games, but not in the single-player mode. If you do not have Xbox Live, then unfortunately the only way to get the armor would be by creating an Xbox Live account (it could be a free trial or a full account) and downloading the armor from there.