I don't know if this is by design or if it's a bug, or an oversight....

If a thief doesn't "study" any thief skills, he can enter any of the
membership guilds unrestricted without paying dues. I quote from the
help file for "Guild Join":

"Joining a guild as a member is something that has been historically taken
for granted. Some guilds are closing their doors to non-members, so
membership is a requirement for entrance to some of the guild halls. When
you join a guild you may receive benefits of such, depending on the guild.
You may join one guild in the land at most and will move to that guild's
city in the process. The price of entrance may vary between guilds.

In order to join a guild, you must find the guildguard of the guild to
become a member. All those under the 10th level will be allowed entrance
to all of their respective guilds, regardless of membership status."

Well at present, the "under 10th level" part is pretty much meaningless
because even beyond 10th level, if a thief hasn't studied any path skills
(including the general "path") he can gain entrance to any guild anyway.
That's not terribly important at higher levels because a thief at higher
levels with no path skills is considerably weaker than a thief who does
have path skills. But in the gauntlet from 11-25, a non-path thief can
be just as strong as a path thief.

n/t