When you attack someone from your guild, kill them or steal from them, you get suspended from the guild until you earn your way back in.

Fighters Guild
Like the other guilds, you are not permitted to steal from, attack or kill
other members of the guild. (Non-members are fair game.) The Fighters Guild
operates on a three-strikes and you're out policy. The first two times you
commit a crime against a guild member, you can earn your way back in. The
third time, you're out for good.

The first time you are expelled, you must bring 20 bear pelts back to Vilena
Donton in Chorrol to be re-instated. The second time you are expelled, you
must bring Donton 20 minotaur horns. Neither are particularly easy tasks,
especially since bears and minotaurs are leveled creatures that only appear
when you're at the right level. That said, you can buy these from shops or steal
them from houses.

MAGES GUILD
The Mages Guild frowns on members who commit crimes against other members. You
get two opportunities to earn your way back into the guild. After the third
crime, you are banned for good.

Earning your way back into the guild depends on the type of crime. You must
bring two types of alchemical ingredients to Raminus Polus, who will
re-instate you into the guild.

Theft: 20 nightshade, 20 mandrake root (find in market district)
Assault: 20 dragon's tongue, 20 redwort flowers (market district)
Murder: 20 vampire dust, 20 daedra hearts (vampire dust can be found in a mine south east of skingrad, near the castle walls) (daedra hearts are found in xilvali and such)

These prices apply regardless of whether it is your first or second offense.

Thieves guild
The Thieves Guild has some pretty strict rules regarding behavior.
(Apparently, there *is* honor among thieves.) You are not to steal from,
assault or kill another guild member. Additionally, you cannot kill anyone
while committing a theft for the guild (unless your doyen or the Gray Fox
specifically gives you permission in advance.)

Unlike the other guilds, getting back into the Thieves Guild is a simple
matter of money. There is a fine attached to each action, and paying the fine
to Armand or S'Krivva gets you back into the guild.

crime | Fine
--------- | --------
Theft | 200
assault | 500
murder | 1,000

* You get charged 1,000 gold Blood Price for each unnecessary murder during a
job. The exceptions are killing one of the two targets of "May the Best Thief
Win", their Blood Price is 500 gold. Your doyen or the Gray Fox will let you
know if any job targets can be killed before you go out on the job.

The Thieves Guild is pretty lenient and always lets you back in, as long as
you pay the fines.

Dark Brotherhood
When you first join the Dark Brotherhood, Lucien Lachance will fill you in on
the Five Tenets:

Tenet 1: Never dishonor the Night Mother. To do so is to invoke the Wrath of
Sithis.

Tenet 2: Never betray the Dark Brotherhood or its secrets. To do so is to
invoke the Wrath of Sithis.

Tenet 3: Never disobey or refuse to carry out an order from a Dark Brotherhood
superior. To do so is to invoke the Wrath of Sithis.

Tenet 4: Never steal the possessions of a Dark Brother or Dark Sister. To do
so is to invoke the Wrath of Sithis.

Tenet 5: Never kill a Dark Brother or Dark Sister. To do so is to invoke the
Wrath of Sithis.

You may wander what this "Wrath of Sithis" is. It is a spirit that will attack
you if you break one of the Tenets. The first two times this happens,
defeating the spirit means you're back in the guild. The third time, defeating
the spirit just means you get to avoid reloading your game. You're out of the
Brotherhood forever.

The first three tenets are impossible to break. The game never gives you a
chance to do any of those things. Well, you can fail to carry out an
assignment, but you're never visited by the Wrath, it just remains an open
quest in your journal. So, basically, you'll only run into a problem if you
steal from or kill another member of the Brotherhood.