Laws must allow revocation:
- Without Conclave, you must have at least Limited Crown Authority, or not be subject to a crown authority law.
- With Conclave, you must have the Revocation Allowed law. Unless you have the Ruler Sovereignty law for revocation, revoking the title without an approving council vote will incur -10 tyranny.
- If tribal and independent, Tribal organization must be at least Limited.
- If tribal and not independent, you probably won't be able to (may be a bug)
The target character must be valid:
- A valid reason is required if you are a republic or have a truce. Otherwise, you may revoke without a valid reason, at the cost of angering your landed vassals (almost as bad as tyranny).
- You cannot revoke titles from a ruler if you have a non-aggression pact.
- Target is your direct vassal (permanently, i.e. not in revolt)
- Target is not your regent
The target title must be valid:
- You cannot usually revoke the last county held by a duke if it is within their de jure duchy; you must revoke the duchy first.
- You must be able to hold the title. Religious head titles can only be held by a character of the correct religion. Khagans cannot revoke clan titles.
- The title is neither contested in, nor the justification for, an ongoing war
- The title was not granted recently (to any character, within the last year)
A claim on the vassal's title allows revoking it.
Certain opinion modifiers allow revoking one title within a limited time:
- a direct vassal who rebelled, and liege won
- a direct vassal who refused to stop backing a plot
- if stacked (failed imprisonment of a character who was already a traitor?), allows revoking all titles instead of just one
- Murderous Traitor (caught while killing my close relative who was under my control)
- Charges of illegitimacy or treachery (from the intrigue focus)
- Declared war
- Has Fatwa Issued
- Witch (mother of demon child)
- Unfaithful wife
- Unfaithful husband (only with full status of women)
Vassals of other religions, if laws allow it:
- Without Conclave: Medium Crown Authority or higher.
- With Conclave: Religious Revoke law
- Tribal infidels and heretics may have their titles revoked by a tribe with Medium Tribal Organization or higher, or by any non-tribal liege regardless of laws.
- Christians can only use these laws to revoke from infidels or heretics, while Indians and Pagans can revoke even from similar religions.
- Other vassals of the same religion will be angry
Special rules for revoking duchies:
- Imperial Administration law allows the Emperor to revoke viceroyal duchies if Charlemagne is enabled or all duchies if not.
- Iqta Government allows feudal Muslim rulers to revoke all ducal-level titles.
Attempting to revoke a title from a vassal:
- Gives the target character an opinion penalty of -60, regardless of whether you have a reason
- Gives all other landed vassals an opinion penalty of -15 if you did not have a valid reason to revoke the title
If the vassal is not in your prison, they choose whether to accept or rebel:
- More likely to rebel if powerful
- More likely to rebel if in a faction ("Rebellious")
- Merchant republics always rebel
Successfully revoking a title:
- Gives the target a claim on the revoked title, which further lowers their opinion of you if you continue to hold the title
- Automatically retracts the vassalage of the de jure vassals of the revoked title
- If they lose their last settlement, higher titles such as duchies are destroyed, and they flee to a foreign court
You may demand that your direct vassal allow one of their vassals to serve you directly. There are two exceptions: you cannot retract baron-tier vassals from their de jure count, and you cannot retract patricians*. Like with title revocation, vassals may refuse by rising in rebellion, unless you hold them as prisoners.
Any valid cause for title revocation can instead be used to retract one vassal. Imperial Administration and Iqta Government allow free retraction of vassals. Nomadic khans don't care if a khagan retracts someone else's vassal.
Retracting a vassal results in a opinion penalty of -45 if the retracted vassal is de jure part of the target's titles and -20 otherwise. If the ruler did not have a reason, their other direct vassals will have opinion penalties of -10 (de jure) or -5.
Revoking titles is a ruler's primary way of dealing with vassals who have gotten too powerful. Vassals who have acquired multiple landed titles can be brought back in line by the ruler getting claims on their titles and revoking them. It also allows getting rid of troublesome vassals who dislike you or whose line of succession would pass the title out of the realm. It can also be used to simply replace vassals with more desirable ones, such as members of your dynasty.
Vassals who rebel when you try to revoke their titles provide the opportunity to revoke two titles without incurring tyranny. Once you've crushed the revolt, revoke a title you don't have a claim on without incurring tyranny because they are a traitor, then revoke the title you do have a claim on. Because the rebels will be imprisoned after losing the war, the opinion penalties are not a problem. Put them in house arrest to retain the benefits of a vassal who can't cause trouble for as long as possible, or throw them in the oubliette so they'll quickly succeed to an heir who doesn't care that you revoked a title.