Actually, we need to consider this further.

It may be possible, for example, that a page is restricted to "premium members". In this case, both Guests and regular members will be restricted. But we may still want a prompt to log in because the user might be one of those premium members.

It may be better to add an additional tick box on the match-key restrictions page; if ticked, then we prompt the user to log in if they are a guest. Or, we always prompt, but we indicate in a message which groups are allowed access (if any).