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Ok. I know this has been talked about a bit as the FAQs have been released. But there seems to be a bit of confusion as to what is and is not allowed and where. So I figured I would start this thread to clarify and for (hopefully) respectful debate (Good luck me!).

So we received this FAQ article (which, you might note, is not actually in any of the FAQs/Errata... great start.)

https://www.warhammer-community.com/2017/07/05/codexes-your-questions-answered-july-5gw-homepage-post-2/

The relevant questions from that article are as follows.

There are a few options that are missing in the codex that appear in the index: why is that? Does that mean I can’t use these models in my army anymore?

While the indexes are designed to cover a long history of miniatures, the codexes are designed to give you rules for the current Warhammer 40,000 range. There are a few options in the indexes for some Characters and vehicles that are no longer represented in the Citadel range – certain Dreadnought weapons that don’t come in the box, or some characters on bikes, for example.
Don’t worry though, you can still use all of these in your games if you have these older models. In these instances, use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).
They still gain all the army wide-bonuses for things like Chapter Tactics and can use Space Marines Stratagems and the like, so such venerable heroes still fit right in with the rest of your army.


Are the rules changing?

Yes, many units’ rules in their codexes will alter from those in the indexes. Sometimes this is to better represent the miniatures and the background, sometimes to balance the game, and sometimes to better fit with the army’s new special rules in the codex itself. In all cases, these will then supersede the rules for that datasheet in the index book.


Can I combine units from the index and a codex into one army?

The datasheets in the new codexes overwrite the same datasheets in the index books. You can certainly use units with updated datasheets alongside units from the index that have yet to be updated. Once a unit has been covered in the codex though, we assume you’re using the latest version.


Can I choose to use the rules and/or points for units from my index instead of the new ones in the codex once released?

In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like.

In all future publications and official events though, it will be assumed that you’re using the most recent rules and Datasheets. It will also be assumed that you’re using the most up to date points for matched play, in this case, those included in the codex.

Now. Some people believe that the first question and answer gives you a blanket justification to use any options that have been removed from a dataslate in any version of the game. I.E. A dread using gun options it doesn't have with the new stats/points costs/ etc etc...

But allow me to provide a counter argument.

In the first question "Don’t worry though, you can still use all of these in your games if you have these older models." requires that
1) you actually have the older model and
2) "In your games" can be read as the same as "In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like."

This is backed by 3 other questions in the same document saying

1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books.
3) In all future publications and official events though, it will be assumed that you’re using the most recent rules and Datasheets.

An option on a datasheet is not itself a datasheet. If the new Dread datasheet does not have the option then, using the most up to date datasheet, you do not have the option. Of course, with permission from your opponent your dread could cost 1ppm and use whatever options you feel like. And if there is no up to date datasheet you can use the ones from the index using the most up to date point values for any options. A Librarian on a Bike for an example, is a different datasheet from a Librarian. So you can still bring a Librarian on a Bike using the Index.


In any game using the actual rules only the options and points and rules for the most up to date datasheet are legal. With opponents permission you can use the older index entries instead. But you are not allowed to pick and choose which dataslate you want to use to get the options you like.



Would you say I am reading this correctly? If not why? Please keep in mind the entire document. The one question does not negate the other 3.

You already understand all the arguments, so you already understand why some will and some won't agree with you. ;-)

There's the 'general versus specific' metric. The general rule is that, if there are two datasheets, you use the most recently published version. In the specific case of a Dreadnought with the twin autocannon loadout that was allowed in previous editions and the Index but not the Codex: use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).

I wonder, has there been a test case for this at the GT?

 lindsay40k wrote:
There's the 'general versus specific' metric. The general rule is that, if there are two datasheets, you use the most recently published version. In the specific case of a Dreadnought with the twin autocannon loadout that was allowed in previous editions and the Index but not the Codex: use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).

I wonder, has there been a test case for this at the GT?

Unfortunately, General Vs Specific was a rule in 7th that does not exist in any 8th document. Which is further complicated by the fact that this FAQ isn't even in the FAQ section. It's just an announcement blurb.

The answer you quote does not say that that dread is legal for matched play or any official game. It just offers a guide line for how to use those options with the release of new books that will likely have points adjustments.

In 3 other answers we are given very explicit instruction in terms of what rules are expected to be used and thus what options the models can legally use.

Unfortunately it's unclear for several reasons.

Firstly those rulings all come from Warhammer community and therefore don't represent faq or errata. Essentially they become indications of RAI not RAW.

Secondly they contradict themselves

BA for example are told to use the index.
The index tells you to use the following SM datasheets
Which the community say are updated by codex SM and you are assumed to be useing the latest version of the data sheet eg the one in codex am
But the community then says BA don't have to use codex SM b

So is it RAW that BA use index datasets
Raw they use SM
Or raw that they may choose

U02dah4 wrote:
Unfortunately it's unclear for several reasons.

Firstly those rulings all come from Warhammer community and therefore don't represent faq or errata. Essentially they become indications of RAI not RAW.

Secondly they contradict themselves

BA for example are told to use the index.
The index tells you to use the following SM datasheets
Which the community say are updated by codex SM and you are assumed to be useing the latest version of the data sheet eg the one in codex am
But the community then says BA don't need codex SM because they should use the index etc etc

Agree partially with your first point, disagree with your second.

While they represent RAI and not RAW because of the reasons you say, it's absolutely clear what they are saying.

It's very clear what BA are supposed to be using right now. The index gives you your army list telling you what datasheets you can use. Some of those Datasheets have a more recent publication in the Codex SM. The legal, current datasheets for those units are in codex SM along with point costs for those units and options. Until a BA publication shows up with a newer more up to date list of rules those are the rules you are supposed to use. It's not contradictory at all and anyone telling you it is is wrong.

While I would personally be happy to have you not have to buy codex SM because just wait for your own and thus would personally be happy to play against your BA with a pure index force if that is your choice (or you know, just get the datasheets you need from some other source for free), legally any datasheets in codex SM that are shared by the BA index army list are the current and legal datasheets for you to use.

From 'Codexes: Your Questions Answered', broken down for clarity:

If I have a Blood Angels, Dark Angels or Space Wolves army, will I need to buy Codex: Space Marines to use my army?

And the answer is..

You don’t have to.

What don't you have to do? You don't have to buy Codex: Space Marines. Why? Because...

Other Space Marines factions not covered in the new codex will continue to use all the datasheets, rules and points values in the index until their own codex is released.

So Blood Angels, Space Wolves, etc. don't use Codex Space Marines for datasheets, rules and points values. What about new models like the Redemptor or Intercessors?

Rules for new models not covered in the index (like the upcoming Redemptor Dreadnought) will be available in the box with the model and matched play points for these units will be made available online.

So GW has been explicitly clear. Blood Angels use the index, not Codex: Space Marines.

 Ghaz wrote:

You don’t have to.

What don't you have to do? You don't have to buy Codex: Space Marines. Why? Because...

Other Space Marines factions not covered in the new codex will continue to use all the datasheets, rules and points values in the index until their own codex is released.

So Blood Angels, Space Wolves, etc. don't use Codex Space Marines for datasheets, rules and points values. What about new models like the Redemptor or Intercessors?

Rules for new models not covered in the index (like the upcoming Redemptor Dreadnought) will be available in the box with the model and matched play points for these units will be made available online.

So GW has been explicitly clear. Blood Angels use the index, not Codex: Space Marines.

I stand corrected.

 Lance845 wrote:
I stand corrected.

And that's one of the rarest statements you'll hear in YMDC

 Lance845 wrote:

 Ghaz wrote:

You don’t have to.

What don't you have to do? You don't have to buy Codex: Space Marines. Why? Because...

Other Space Marines factions not covered in the new codex will continue to use all the datasheets, rules and points values in the index until their own codex is released.

So Blood Angels, Space Wolves, etc. don't use Codex Space Marines for datasheets, rules and points values. What about new models like the Redemptor or Intercessors?

Rules for new models not covered in the index (like the upcoming Redemptor Dreadnought) will be available in the box with the model and matched play points for these units will be made available online.

So GW has been explicitly clear. Blood Angels use the index, not Codex: Space Marines.

I stand corrected.

Except thats a cherry pick from self same page your quoting from

"In all future publications and official events though, it will be assumed that you’re using the most recent rules and Datasheets. It will also be assumed that you’re using the most up to date points for matched play, in this case, those included in the codex."

While if you follow their direction the rules in the index itself in the BA section tells you explicitly to use the SM datasheets not the SM datasheets in the index. The current version of which is in codex SM.

As you say it also says you "don't have to" not you can't .

Which is where I come back to its not clear I understand and recognise ghaz''s interpretation as potentially valid under RAI from Warhammer community that you should only use index datasheets . I also recognise lances interpretation as valid under RAI as the community site is clear they update the datasheets. I also think there's a middle ground under RAI due to the "don't have to" and maybe you can do either so yes RAI in this instance seems unclear

RAW however as covered in detail in the tech marine thread is you use the SM datasheets which are now in the codex that is clear.

So if RAI is unclear and RAW is clear I go with RAW

Automatically Appended Next Post:

U02dah4 wrote:

 Lance845 wrote:

 Ghaz wrote:

You don’t have to.

What don't you have to do? You don't have to buy Codex: Space Marines. Why? Because...

Other Space Marines factions not covered in the new codex will continue to use all the datasheets, rules and points values in the index until their own codex is released.

So Blood Angels, Space Wolves, etc. don't use Codex Space Marines for datasheets, rules and points values. What about new models like the Redemptor or Intercessors?

Rules for new models not covered in the index (like the upcoming Redemptor Dreadnought) will be available in the box with the model and matched play points for these units will be made available online.

So GW has been explicitly clear. Blood Angels use the index, not Codex: Space Marines.

I stand corrected.

Except thats a cherry pick from self same page your quoting from

"In all future publications and official events though, it will be assumed that you’re using the most recent rules and Datasheets. It will also be assumed that you’re using the most up to date points for matched play, in this case, those included in the codex."

While if you follow their direction the rules in the index itself in the BA section tells you explicitly to use the SM datasheets not the SM datasheets in the index. The current version of which is in codex SM.

As you say it also says you "don't have to" not you can't .

Which is where I come back to its not clear I understand and recognise ghaz''s interpretation as potentially valid under RAI from Warhammer community that you should only use index datasheets . I also recognise lances interpretation as valid under RAI as the community site is clear they update the datasheets. I also think there's a middle ground under RAI due to the "don't have to" and maybe you can do either so yes RAI in this instance seems unclear

RAW however as covered in detail in the tech marine thread is you use the SM datasheets which are now in the codex that is clear.

So if RAI is unclear and RAW is clear I go with RAW

I get what your saying for forces that do not yet have a codex. I hear ya.

It's also a problem that will work itself out over time. We will all have codexes eventually. But in terms of forces that DO have a codex (which will be all of us much faster then it has ever been in the past), do we agree that you have to use the codex datasheet?

Like... a upcoming example.

1) If Tyranid Shrikes are not in the codex then you are free to use the index datasheet for Shrikes. If Bone Swords points change in the codex then you pay codex prices using the codex profile for Index Shrikes Bone Swords.

2) If Hive Tyrants are in the codex then you have to use the codex datasheet for the HT. If the Codex HT does not have the option to take Massive Rending Claws then you are not allowed to use MRC with HTs.

 Lance845 wrote:
I get what your saying for forces that do not yet have a codex. I hear ya.

But in terms of forces that DO have a codex (which will be all of us eventually... and much faster then it has ever been in the past), do we agree that you have to use the codex datasheet?

Like... a upcoming example.

1) If Tyranid Shrikes are not in the codex then you are free to use the index datasheet for Shrikes. If Bone Swords points change in the codex then you pay codex prices using the codex profile for Index Shrikes Bone Swords.

2) If Hive Tyrants are in the codex then you have to use the codex datasheet for the HT. If the Codex HT does not have the option to take Massive Rending Claws then you are not allowed to use MRC with HTs.

i agree with both of these.

 Lance845 wrote:

It's also a problem that will work itself out over time. We will all have codexes eventually. But in terms of forces that DO have a codex (which will be all of us much faster then it has ever been in the past), do we agree that you have to use the codex datasheet?

Like... a upcoming example.

1) If Tyranid Shrikes are not in the codex then you are free to use the index datasheet for Shrikes. If Bone Swords points change in the codex then you pay codex prices using the codex profile for Index Shrikes Bone Swords.

2) If Hive Tyrants are in the codex then you have to use the codex datasheet for the HT. If the Codex HT does not have the option to take Massive Rending Claws then you are not allowed to use MRC with HTs.

I disagree with 2.

https://www.warhammer-community.com/2017/07/05/codexes-your-questions-answered-july-5gw-homepage-post-2/

There are a few options that are missing in the codex that appear in the index: why is that? Does that mean I can’t use these models in my army anymore?
While the indexes are designed to cover a long history of miniatures, the codexes are designed to give you rules for the current Warhammer 40,000 range. There are a few options in the indexes for some Characters and vehicles that are no longer represented in the Citadel range – certain Dreadnought weapons that don’t come in the box, or some characters on bikes, for example.
Don’t worry though, you can still use all of these in your games if you have these older models. In these instances, use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).
They still gain all the army wide-bonuses for things like Chapter Tactics and can use Space Marines Stratagems and the like, so such venerable heroes still fit right in with the rest of your army.

If the HT has MRC in the index you can still use him with index points, because its the most recent points published.

p5freak wrote:

 Lance845 wrote:

It's also a problem that will work itself out over time. We will all have codexes eventually. But in terms of forces that DO have a codex (which will be all of us much faster then it has ever been in the past), do we agree that you have to use the codex datasheet?

Like... a upcoming example.

1) If Tyranid Shrikes are not in the codex then you are free to use the index datasheet for Shrikes. If Bone Swords points change in the codex then you pay codex prices using the codex profile for Index Shrikes Bone Swords.

2) If Hive Tyrants are in the codex then you have to use the codex datasheet for the HT. If the Codex HT does not have the option to take Massive Rending Claws then you are not allowed to use MRC with HTs.

I disagree with 2.

https://www.warhammer-community.com/2017/07/05/codexes-your-questions-answered-july-5gw-homepage-post-2/

There are a few options that are missing in the codex that appear in the index: why is that? Does that mean I can’t use these models in my army anymore?
While the indexes are designed to cover a long history of miniatures, the codexes are designed to give you rules for the current Warhammer 40,000 range. There are a few options in the indexes for some Characters and vehicles that are no longer represented in the Citadel range – certain Dreadnought weapons that don’t come in the box, or some characters on bikes, for example.
Don’t worry though, you can still use all of these in your games if you have these older models. In these instances, use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).
They still gain all the army wide-bonuses for things like Chapter Tactics and can use Space Marines Stratagems and the like, so such venerable heroes still fit right in with the rest of your army.

If the HT has MRC in the index you can still use him with index points, because its the most recent points published.

That quote is in the OP, along with 3 others from the same document that say that you are expected to use the most up to date Datasheet. Not just use it, but that the most up to date datasheet completely replaces it. It supersedes it as though the index one never existed. If the most up to date Datasheet does not give you the option then you don't have it.

 Lance845 wrote:

That quote is in the OP, along with 3 others from the same document that say that you are expected to use the most up to date Datasheet. If the most up to date Datasheet does not give you the option then you don't have it.

Just because its missing in the most up to date datasheet (codex) doesnt mean you cant use it anymore.
Don’t worry though, you can still use all of these in your games if you have these older models. In these instances, use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).

This clearly says you can still use the model with index points.

p5freak wrote:

 Lance845 wrote:

That quote is in the OP, along with 3 others from the same document that say that you are expected to use the most up to date Datasheet. If the most up to date Datasheet does not give you the option then you don't have it.

Just because its missing in the most up to date datasheet (codex) doesnt mean you cant use it anymore.

Don’t worry though, you can still use all of these in your games if you have these older models. In these instances, use the datasheet from the index, and the most recent points published for that model and its weapons (currently, also in the index).

This clearly says you can still use the model with index points.

In the first question "Don’t worry though, you can still use all of these in your games if you have these older models." requires that
1) you actually have the older model and
2) "In your games" can be read as the same as "In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like."

This is backed by 3 other questions in the same document saying

1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books.
3) In all future publications and official events though, it will be assumed that you’re using the most recent rules and Datasheets.

And the rest of the document makes it very clear that in your own personal games where you and your opponent agree you can do whatever you want. But in any game using official rules you don't get the option. Only the most recent datasheet and any of the rules on it matter. Which includes the options for wargear.

That one quote does not exist in a vacuum. You cannot take it by itself. You need to take a look at the whole document.

Again: has there been a test case, most likely a Dreadnought with a twin Autocannon?

This thread is just a repeat of others tbh

 Lance845 wrote:

And the rest of the document makes it very clear that in your own personal games where you and your opponent agree you can do whatever you want. But in any game using official rules you don't get the option. Only the most recent datasheet and any of the rules on it matter. Which includes the options for wargear.

No, it doesn't make it clear. That is what you are reading into it, but it doesn't make it "very clear". It only makes it your interpretation. Another option is that they meant what they said about still being able to use your model in your games, which would presumably also mean "any game using official rules". Until we have a test case at a tournament that doesn't let you use the model, it looks like you do have permission to use the model despite what you say.

 doctortom wrote:

 Lance845 wrote:

And the rest of the document makes it very clear that in your own personal games where you and your opponent agree you can do whatever you want. But in any game using official rules you don't get the option. Only the most recent datasheet and any of the rules on it matter. Which includes the options for wargear.

No, it doesn't make it clear. That is what you are reading into it, but it doesn't make it "very clear". It only makes it your interpretation. Another option is that they meant what they said about still being able to use your model in your games, which would presumably also mean "any game using official rules". Until we have a test case at a tournament that doesn't let you use the model, it looks like you do have permission to use the model despite what you say.

True enough. As it is, the bigger tournaments tend to change some rules as it is in order to attract as many good players as possible, so using them as a benchmark for "official games" is a bit of a pointless task.

 Charistoph wrote:

 doctortom wrote:

 Lance845 wrote:

And the rest of the document makes it very clear that in your own personal games where you and your opponent agree you can do whatever you want. But in any game using official rules you don't get the option. Only the most recent datasheet and any of the rules on it matter. Which includes the options for wargear.

No, it doesn't make it clear. That is what you are reading into it, but it doesn't make it "very clear". It only makes it your interpretation. Another option is that they meant what they said about still being able to use your model in your games, which would presumably also mean "any game using official rules". Until we have a test case at a tournament that doesn't let you use the model, it looks like you do have permission to use the model despite what you say.

True enough. As it is, the bigger tournaments tend to change some rules as it is in order to attract as many good players as possible, so using them as a benchmark for "official games" is a bit of a pointless task.

True enough.

Yeah since the tournys more or less run on house rules it doesn't prove much of anything.

But, as to my argument being unclear,


1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books.

These statements are very definitive. They are VERY clear. There is no question as to their intent.

What is unclear to you about IN ALL CASES and OVERWRITE?

 lindsay40k wrote:
Again: has there been a test case, most likely a Dreadnought with a twin Autocannon?

I am of the opinion that due to the contradictory nature of the GW statements, that a Venerable Dread with AutoCannon/Lascanon setup is no longer legal for Codex: Space Marines armies, due to the instruction to use the newest datasheet where possible, while things like Veterans on Bikes are legal because there is no datasheet in the codex for them, so you default to the Index.

I would like if GW made it explicitly clear: "Use the codex rules and points. If a unit or loadout doesn't exist in the codex, use ONLY the index rules and points." Such a simple instruction that GW has characteristically botched up.

 Lance845 wrote:
Yeah since the tournys more or less run on house rules it doesn't prove much of anything.

But, as to my argument being unclear,


1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books.

These statements are very definitive. They are VERY clear. There is no question as to their intent.

What is unclear to you about IN ALL CASES and OVERWRITE?

The part where it says you can still use your old models when there's a combination not used in the new codex. "You may still use your models" is equally clear, yet contradicts what you are saying here.


I am not saying your argument is incorrect, not that you weren't clear. You were clearly incorrect.

 doctortom wrote:


The part where it says you can still use your old models when there's a combination not used in the new codex. "You may still use your models" is equally clear, yet contradicts what you are saying here.


I am not saying your argument is incorrect, not that you weren't clear. You were clearly incorrect.

"In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like."

They have never said you were incapable of using your models. They said you needed your opponents agreement.

 Lance845 wrote:

 doctortom wrote:


The part where it says you can still use your old models when there's a combination not used in the new codex. "You may still use your models" is equally clear, yet contradicts what you are saying here.


I am not saying your argument is incorrect, not that you weren't clear. You were clearly incorrect.

"In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like."

They have never said you were incapable of using your models. They said you needed your opponents agreement.

You said "1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books. "

You said "in all cases" - how do you get to use your models if "in all cases" you don't get to access the sheet that has the rules for your old model? You contradict yourself.

 doctortom wrote:

 Lance845 wrote:

 doctortom wrote:


The part where it says you can still use your old models when there's a combination not used in the new codex. "You may still use your models" is equally clear, yet contradicts what you are saying here.


I am not saying your argument is incorrect, not that you weren't clear. You were clearly incorrect.

"In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like."

They have never said you were incapable of using your models. They said you needed your opponents agreement.

You said "1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books. "

You said "in all cases" - how do you get to use your models if "in all cases" you don't get to access the sheet that has the rules for your old model? You contradict yourself.

I do not. Officially, or in other words in any way in which the game is being played with legally supported rules, the datasheet replaces the index one and the index one is no longer valid. But "In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like.".

The stance we have is, go set up a table and have fun. If you got the model and you want to use the index rules and your opponent is cool then have a ball. But when the codex is released with a updated version of the datasheet that new datasheet is there to replace the old one in all cases. In any official event you will be expected to use the most current datasheets. For the sake of balance, updating the model range, or more accurately representing the current fluff of the game the new datasheet is the only one that matters and the one you are assumed to be using.

You are allowed to house rule. The game is built with 3 ways to play and open is very specifically about you and your opponent doing whatever you like. In your own games you are welcome to mix and match whatever! But in matched the only legal datasheet is the most current.

You cannot bring options to Matched that do not exist on the most current datasheet. If you do it's not matched, it's open using most of matched plays rules.

 Lance845 wrote:

 doctortom wrote:

 Lance845 wrote:

 doctortom wrote:


The part where it says you can still use your old models when there's a combination not used in the new codex. "You may still use your models" is equally clear, yet contradicts what you are saying here.


I am not saying your argument is incorrect, not that you weren't clear. You were clearly incorrect.

"In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like."

They have never said you were incapable of using your models. They said you needed your opponents agreement.

You said "1) In all cases, these will then supersede the rules for that datasheet in the index book.
2) The datasheets in the new codexes overwrite the same datasheets in the index books. "

You said "in all cases" - how do you get to use your models if "in all cases" you don't get to access the sheet that has the rules for your old model? You contradict yourself.

I do not. Officially, or in other words in any way in which the game is being played with legally supported rules, the datasheet replaces the index one and the index one is no longer valid. But "In your own games, if you and your opponent agree, you can, of course, play with whatever rules you like.".

The stance we have is, go set up a table and have fun. If you got the model and you want to use the index rules and your opponent is cool then have a ball. But when the codex is released with a updated version of the datasheet that new datasheet is there to replace the old one in all cases. In any official event you will be expected to use the most current datasheets. For the sake of balance, updating the model range, or more accurately representing the current fluff of the game the new datasheet is the only one that matters and the one you are assumed to be using.

You are allowed to house rule. The game is built with 3 ways to play and open is very specifically about you and your opponent doing whatever you like. In your own games you are welcome to mix and match whatever! But in matched the only legal datasheet is the most current.

You cannot bring options to Matched that do not exist on the most current datasheet. If you do it's not matched, it's open using most of matched plays rules.

Nope, sorry, but you are wrong.

"Don’t worry though, you can still use all of these in your games if you have these older models. " It does not say that it your opponent must agree to it. It does not state that this does not apply to Matched play. This does not state that you may not do this in "official" games. All you are told is that you may use your older models with configurations not supported by the updated codexes, in which case you use the index. If you have a configuration that is supported by the codex, then yes you use the codex. If it's an older model not supported by the codex but is supported by the index, you have blanket permission to use that model with the index rules and updated costs.

A quote taken out of context that ignores the rest of the document is meaningless.

 Lance845 wrote:
A quote taken out of context that ignores the rest of the document is meaningless.

Which can also apply to what you are saying.