Do I lose access to a feat if ability drain results in no longer meeting the prerequisite?

Question

Do curses or ability damage/drain cause a character to be unable to use his feats?

For example, a Ranger with 20 Dex who has two-weapon-fighting feats and is using two weapons gets cursed or ability drained and his Dex drops to 14. Does that cause the character not to be able to use his two-weapon feats (which have a requirement of at least 15 Dex)?

What about his other feats that have prerequisites of blocked feats? (As another example: a fighter with the Whirlwind Attack feat, which requires Combat Expertise gets an INT penalty that drops his INT under 13, a prerequisite of Combat Expertise). I think that he can no longer use his Combat Expertise feat (because of low INT) and also Whirlwind Attack and any other feats that require Combat Expertise. Is that right?

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I guess it is better to clarify the reason I am asking.

First of all, there are so many books, and there are too many authors that create them and test them. Many bugs are uncovered due to that reason. It is quite hard to keep track of all these things. I know that.

The reason for the question is, for higher-level builds, skill, feat, class, prestige class, template and ability score choices become more important. And there are casters, whose main combat skills depend on spells (clerics, sorcerers, and wizards, especially). Maybe druids can deal with key ability score penalties, and clerics may try to survive such conditions. Wizards and sorcerers have less of a chance when their key ability score drops. A curse may cause them to be without magic (or with some weak spells) if they fail to resist it. They probably have higher Will saves, but they all have the chance.

And I am trying to be sure about the situation of a warrior-based class, because feats mean a lot to them. So what happens when they get cursed? Failure to be able to use a key feat is important, but not as much as a wizard who is unable to cast spells.

Related FAQ answer is not enough about this situation (the following part)

A feat sometimes requires you to have a certain ability score, which is the case with Two-Weapon Fighting (it requires Dex 15). A character has, say, Dex 13, but wears an item, in this case gloves of Dexterity +2, and now her Dex score is 15. Can she take the feat and have it be active only when she wears the item?

Actually yes, she could take the feat, but she would lose the use of the feat if, for whatever reason, she loses the bonus from the item.

So, still looking for something more satisfactory.

UPDATE: @LitheOhm's answer:

Players Handbook:

Two-Weapon Fighting
Prerequisite: Dex 15.

Complete Adventurer

Oversized Two-Weapon Fighting
Prerequisite: Str13, Two-Weapon Fighting

I wish to clarify that, I just wish to be sure about what to do in such situation. That is just an example and probably being able to use Oversized Two-Weapon Fighting feat will not save the character while he could not use basic Two-Weapon Fighting feats due to Lowered DEX. But I still wonder, whether he could still use Oversized Two-Weapon Fighting.

Of course there could be some other feats which fits that situation. That is just one I noticed.

Answer 1

Yes: curses, ability damage, and ability drain causes loss of the ability to use the feat. You don't actually lose the feat, however - you just don't gain it's benefits until you meet the prerequisite again.

From the Players Handbook 3.5 page 87.

Prerequisites

A character cannot use a feat if he or she has lost the prerequisite. For example, if your characters strength drops below 13 because of a ray of enfeeblement spell, he or she can't use the Power Attack feat until the prerequisite is met again

When you lose a feat that is a prerequisite of another feat only the abilities of the prerequisite feat are lost, because you only have to have a prerequisite feat to qualify for another feat and losing the abilities doesn't change the fact that you have the prerequisite feat, you don't actually have to be able to use the prerequisite feat to qualify for the other feat...

...So if your dexterity was dropped below 13 you would lose access to Two-Weapon-Fighting but you would not lose access to Oversized-Two-Weapon-Fighting.

Answer 2

This depends on the feat in question. However simply losing access to a lower-level feat by itself isn't enough to remove access to other feats which have that as a prerequisite.

Take power attack, cleave and great cleave for example. Each requires a strength of 13 or higher to use. In this instance since a player with less than strength 13 (temporary or drain) lacks the ability to use those feats then he fails to meet the prerequisites for each of them, despite having the feats. Strength must be raised before any of them become available for use. The same goes for every power attack tree feat on the SRD.

Examine deflect arrows and snatch arrows next. Many feats follow this suit - the lower level feat requires a lower score in that prerequisite ability while the higher level feat requires a higher score. In that instance the player would lose access first to the higher level and then to the lower level as the related ability score is lowered, dexterity in this case.

As cited in the question whirlwind attack requires combat expertise. It also has a prerequisite of intelligence 13 though, so the prerequisite stands.

Metamagic spells take up a higher level spell slot and in order to cast any spell a caster must have an appropriate ability score of at least 10+spell level. If my wizard's intelligence is drained to 15 he could still cast fireball (3rd level) but he could not maximize that same fireball (6th level spell slot).

They could fight with two weapons if their dex was drained below the prerequisite 15 for two-weapon fighting. Notice which penalties would apply. They wouldn't be able to use their 2-weapon fighting feat. The oversized 2 weapon feat would help them by having them use the second row of the two-weapon fighting table (-4/-8) when wielding two one-handed weapons but it would not bring them to the bottom row of (-2/-2).

Oversized doesn't grant you the ability to fight with two weapons - it reduces the penalty for using a one-handed weapon instead of a light weapon in your off-hand. Two-weapon fighting feat constraint still applies.