Forgeworld Knights being used in Codex: IK
So this has come up a bunch lately on FB, and like most GW/FW rules, I have yet to see anyone with a definitive lay on what the exact ruling should be. The most recent appearance of this was in an AdMech group, and after I laid down what I felt was a very compelling argument, the other guy said 'well, I'm bored of this, so I'm just going to use the RAW'.
The Cerastus-class knights that Forgeworld has created all have a rule attached to them that state that in any Codex: Imperial Knights army (which means Oathsworn or Household Detachment, Exalted Court Formation, or Baronial Court Formation), you can not have more of <insert this Knight's name here> than any other knight.
The biggest time this issue crops up is with the Oathsworn Detachment, which allows 1-3 knights. It's especially prevalent now with the AdMech War Convocation.
My argument is that if you're using an Oathsworn, and you only ran ONE single knight, then it could not be any of the Cerastus-class knights, because by having one, you would have more of that knight than any other.
Other people have argued that by only having one knight, there are no other knights to compare to, therefore the rule does not apply.
(And yes, I will admit that ITC has gone with that ruling, stating you are allowed one FW knight in an Oathsworn on its own.)
Ignoring ITC, since really, that's just a tournament with its own homebrew rules, I'd like to hear people's opinions on this.
TL;DR - 1 > 0, you can't have a FW knight by itself.